linux-next/fs/xfs/xfs_log_cil.c
Uros Bizjak 214093534f xfs: Use xchg() in xlog_cil_insert_pcp_aggregate()
try_cmpxchg() loop with constant "new" value can be substituted
with just xchg() to atomically get and clear the location.

The code on x86_64 improves from:

    1e7f:	48 89 4c 24 10       	mov    %rcx,0x10(%rsp)
    1e84:	48 03 14 c5 00 00 00 	add    0x0(,%rax,8),%rdx
    1e8b:	00
			1e88: R_X86_64_32S	__per_cpu_offset
    1e8c:	8b 02                	mov    (%rdx),%eax
    1e8e:	41 89 c5             	mov    %eax,%r13d
    1e91:	31 c9                	xor    %ecx,%ecx
    1e93:	f0 0f b1 0a          	lock cmpxchg %ecx,(%rdx)
    1e97:	75 f5                	jne    1e8e <xlog_cil_commit+0x84e>
    1e99:	48 8b 4c 24 10       	mov    0x10(%rsp),%rcx
    1e9e:	45 01 e9             	add    %r13d,%r9d

to just:

    1e7f:	48 03 14 cd 00 00 00 	add    0x0(,%rcx,8),%rdx
    1e86:	00
			1e83: R_X86_64_32S	__per_cpu_offset
    1e87:	31 c9                	xor    %ecx,%ecx
    1e89:	87 0a                	xchg   %ecx,(%rdx)
    1e8b:	41 01 cb             	add    %ecx,%r11d

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Chandan Babu R <chandan.babu@oracle.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <elder@riscstar.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
2024-11-28 12:42:10 +01:00

1988 lines
62 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2010 Red Hat, Inc. All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_shared.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_extent_busy.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"
#include "xfs_trace.h"
#include "xfs_discard.h"
/*
* Allocate a new ticket. Failing to get a new ticket makes it really hard to
* recover, so we don't allow failure here. Also, we allocate in a context that
* we don't want to be issuing transactions from, so we need to tell the
* allocation code this as well.
*
* We don't reserve any space for the ticket - we are going to steal whatever
* space we require from transactions as they commit. To ensure we reserve all
* the space required, we need to set the current reservation of the ticket to
* zero so that we know to steal the initial transaction overhead from the
* first transaction commit.
*/
static struct xlog_ticket *
xlog_cil_ticket_alloc(
struct xlog *log)
{
struct xlog_ticket *tic;
tic = xlog_ticket_alloc(log, 0, 1, 0);
/*
* set the current reservation to zero so we know to steal the basic
* transaction overhead reservation from the first transaction commit.
*/
tic->t_curr_res = 0;
tic->t_iclog_hdrs = 0;
return tic;
}
static inline void
xlog_cil_set_iclog_hdr_count(struct xfs_cil *cil)
{
struct xlog *log = cil->xc_log;
atomic_set(&cil->xc_iclog_hdrs,
(XLOG_CIL_BLOCKING_SPACE_LIMIT(log) /
(log->l_iclog_size - log->l_iclog_hsize)));
}
/*
* Check if the current log item was first committed in this sequence.
* We can't rely on just the log item being in the CIL, we have to check
* the recorded commit sequence number.
*
* Note: for this to be used in a non-racy manner, it has to be called with
* CIL flushing locked out. As a result, it should only be used during the
* transaction commit process when deciding what to format into the item.
*/
static bool
xlog_item_in_current_chkpt(
struct xfs_cil *cil,
struct xfs_log_item *lip)
{
if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
return false;
/*
* li_seq is written on the first commit of a log item to record the
* first checkpoint it is written to. Hence if it is different to the
* current sequence, we're in a new checkpoint.
*/
return lip->li_seq == READ_ONCE(cil->xc_current_sequence);
}
bool
xfs_log_item_in_current_chkpt(
struct xfs_log_item *lip)
{
return xlog_item_in_current_chkpt(lip->li_log->l_cilp, lip);
}
/*
* Unavoidable forward declaration - xlog_cil_push_work() calls
* xlog_cil_ctx_alloc() itself.
*/
static void xlog_cil_push_work(struct work_struct *work);
static struct xfs_cil_ctx *
xlog_cil_ctx_alloc(void)
{
struct xfs_cil_ctx *ctx;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
INIT_LIST_HEAD(&ctx->committing);
INIT_LIST_HEAD(&ctx->busy_extents.extent_list);
INIT_LIST_HEAD(&ctx->log_items);
INIT_LIST_HEAD(&ctx->lv_chain);
INIT_WORK(&ctx->push_work, xlog_cil_push_work);
return ctx;
}
/*
* Aggregate the CIL per cpu structures into global counts, lists, etc and
* clear the percpu state ready for the next context to use. This is called
* from the push code with the context lock held exclusively, hence nothing else
* will be accessing or modifying the per-cpu counters.
*/
static void
xlog_cil_push_pcp_aggregate(
struct xfs_cil *cil,
struct xfs_cil_ctx *ctx)
{
struct xlog_cil_pcp *cilpcp;
int cpu;
for_each_cpu(cpu, &ctx->cil_pcpmask) {
cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
ctx->ticket->t_curr_res += cilpcp->space_reserved;
cilpcp->space_reserved = 0;
if (!list_empty(&cilpcp->busy_extents)) {
list_splice_init(&cilpcp->busy_extents,
&ctx->busy_extents.extent_list);
}
if (!list_empty(&cilpcp->log_items))
list_splice_init(&cilpcp->log_items, &ctx->log_items);
/*
* We're in the middle of switching cil contexts. Reset the
* counter we use to detect when the current context is nearing
* full.
*/
cilpcp->space_used = 0;
}
}
/*
* Aggregate the CIL per-cpu space used counters into the global atomic value.
* This is called when the per-cpu counter aggregation will first pass the soft
* limit threshold so we can switch to atomic counter aggregation for accurate
* detection of hard limit traversal.
*/
static void
xlog_cil_insert_pcp_aggregate(
struct xfs_cil *cil,
struct xfs_cil_ctx *ctx)
{
int cpu;
int count = 0;
/* Trigger atomic updates then aggregate only for the first caller */
if (!test_and_clear_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags))
return;
/*
* We can race with other cpus setting cil_pcpmask. However, we've
* atomically cleared PCP_SPACE which forces other threads to add to
* the global space used count. cil_pcpmask is a superset of cilpcp
* structures that could have a nonzero space_used.
*/
for_each_cpu(cpu, &ctx->cil_pcpmask) {
struct xlog_cil_pcp *cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
count += xchg(&cilpcp->space_used, 0);
}
atomic_add(count, &ctx->space_used);
}
static void
xlog_cil_ctx_switch(
struct xfs_cil *cil,
struct xfs_cil_ctx *ctx)
{
xlog_cil_set_iclog_hdr_count(cil);
set_bit(XLOG_CIL_EMPTY, &cil->xc_flags);
set_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags);
ctx->sequence = ++cil->xc_current_sequence;
ctx->cil = cil;
cil->xc_ctx = ctx;
}
/*
* After the first stage of log recovery is done, we know where the head and
* tail of the log are. We need this log initialisation done before we can
* initialise the first CIL checkpoint context.
*
* Here we allocate a log ticket to track space usage during a CIL push. This
* ticket is passed to xlog_write() directly so that we don't slowly leak log
* space by failing to account for space used by log headers and additional
* region headers for split regions.
*/
void
xlog_cil_init_post_recovery(
struct xlog *log)
{
log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
log->l_cilp->xc_ctx->sequence = 1;
xlog_cil_set_iclog_hdr_count(log->l_cilp);
}
static inline int
xlog_cil_iovec_space(
uint niovecs)
{
return round_up((sizeof(struct xfs_log_vec) +
niovecs * sizeof(struct xfs_log_iovec)),
sizeof(uint64_t));
}
/*
* Allocate or pin log vector buffers for CIL insertion.
*
* The CIL currently uses disposable buffers for copying a snapshot of the
* modified items into the log during a push. The biggest problem with this is
* the requirement to allocate the disposable buffer during the commit if:
* a) does not exist; or
* b) it is too small
*
* If we do this allocation within xlog_cil_insert_format_items(), it is done
* under the xc_ctx_lock, which means that a CIL push cannot occur during
* the memory allocation. This means that we have a potential deadlock situation
* under low memory conditions when we have lots of dirty metadata pinned in
* the CIL and we need a CIL commit to occur to free memory.
*
* To avoid this, we need to move the memory allocation outside the
* xc_ctx_lock, but because the log vector buffers are disposable, that opens
* up a TOCTOU race condition w.r.t. the CIL committing and removing the log
* vector buffers between the check and the formatting of the item into the
* log vector buffer within the xc_ctx_lock.
*
* Because the log vector buffer needs to be unchanged during the CIL push
* process, we cannot share the buffer between the transaction commit (which
* modifies the buffer) and the CIL push context that is writing the changes
* into the log. This means skipping preallocation of buffer space is
* unreliable, but we most definitely do not want to be allocating and freeing
* buffers unnecessarily during commits when overwrites can be done safely.
*
* The simplest solution to this problem is to allocate a shadow buffer when a
* log item is committed for the second time, and then to only use this buffer
* if necessary. The buffer can remain attached to the log item until such time
* it is needed, and this is the buffer that is reallocated to match the size of
* the incoming modification. Then during the formatting of the item we can swap
* the active buffer with the new one if we can't reuse the existing buffer. We
* don't free the old buffer as it may be reused on the next modification if
* it's size is right, otherwise we'll free and reallocate it at that point.
*
* This function builds a vector for the changes in each log item in the
* transaction. It then works out the length of the buffer needed for each log
* item, allocates them and attaches the vector to the log item in preparation
* for the formatting step which occurs under the xc_ctx_lock.
*
* While this means the memory footprint goes up, it avoids the repeated
* alloc/free pattern that repeated modifications of an item would otherwise
* cause, and hence minimises the CPU overhead of such behaviour.
*/
static void
xlog_cil_alloc_shadow_bufs(
struct xlog *log,
struct xfs_trans *tp)
{
struct xfs_log_item *lip;
list_for_each_entry(lip, &tp->t_items, li_trans) {
struct xfs_log_vec *lv;
int niovecs = 0;
int nbytes = 0;
int buf_size;
bool ordered = false;
/* Skip items which aren't dirty in this transaction. */
if (!test_bit(XFS_LI_DIRTY, &lip->li_flags))
continue;
/* get number of vecs and size of data to be stored */
lip->li_ops->iop_size(lip, &niovecs, &nbytes);
/*
* Ordered items need to be tracked but we do not wish to write
* them. We need a logvec to track the object, but we do not
* need an iovec or buffer to be allocated for copying data.
*/
if (niovecs == XFS_LOG_VEC_ORDERED) {
ordered = true;
niovecs = 0;
nbytes = 0;
}
/*
* We 64-bit align the length of each iovec so that the start of
* the next one is naturally aligned. We'll need to account for
* that slack space here.
*
* We also add the xlog_op_header to each region when
* formatting, but that's not accounted to the size of the item
* at this point. Hence we'll need an addition number of bytes
* for each vector to hold an opheader.
*
* Then round nbytes up to 64-bit alignment so that the initial
* buffer alignment is easy to calculate and verify.
*/
nbytes += niovecs *
(sizeof(uint64_t) + sizeof(struct xlog_op_header));
nbytes = round_up(nbytes, sizeof(uint64_t));
/*
* The data buffer needs to start 64-bit aligned, so round up
* that space to ensure we can align it appropriately and not
* overrun the buffer.
*/
buf_size = nbytes + xlog_cil_iovec_space(niovecs);
/*
* if we have no shadow buffer, or it is too small, we need to
* reallocate it.
*/
if (!lip->li_lv_shadow ||
buf_size > lip->li_lv_shadow->lv_size) {
/*
* We free and allocate here as a realloc would copy
* unnecessary data. We don't use kvzalloc() for the
* same reason - we don't need to zero the data area in
* the buffer, only the log vector header and the iovec
* storage.
*/
kvfree(lip->li_lv_shadow);
lv = xlog_kvmalloc(buf_size);
memset(lv, 0, xlog_cil_iovec_space(niovecs));
INIT_LIST_HEAD(&lv->lv_list);
lv->lv_item = lip;
lv->lv_size = buf_size;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];
lip->li_lv_shadow = lv;
} else {
/* same or smaller, optimise common overwrite case */
lv = lip->li_lv_shadow;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
lv->lv_buf_len = 0;
lv->lv_bytes = 0;
}
/* Ensure the lv is set up according to ->iop_size */
lv->lv_niovecs = niovecs;
/* The allocated data region lies beyond the iovec region */
lv->lv_buf = (char *)lv + xlog_cil_iovec_space(niovecs);
}
}
/*
* Prepare the log item for insertion into the CIL. Calculate the difference in
* log space it will consume, and if it is a new item pin it as well.
*/
STATIC void
xfs_cil_prepare_item(
struct xlog *log,
struct xfs_log_vec *lv,
struct xfs_log_vec *old_lv,
int *diff_len)
{
/* Account for the new LV being passed in */
if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
*diff_len += lv->lv_bytes;
/*
* If there is no old LV, this is the first time we've seen the item in
* this CIL context and so we need to pin it. If we are replacing the
* old_lv, then remove the space it accounts for and make it the shadow
* buffer for later freeing. In both cases we are now switching to the
* shadow buffer, so update the pointer to it appropriately.
*/
if (!old_lv) {
if (lv->lv_item->li_ops->iop_pin)
lv->lv_item->li_ops->iop_pin(lv->lv_item);
lv->lv_item->li_lv_shadow = NULL;
} else if (old_lv != lv) {
ASSERT(lv->lv_buf_len != XFS_LOG_VEC_ORDERED);
*diff_len -= old_lv->lv_bytes;
lv->lv_item->li_lv_shadow = old_lv;
}
/* attach new log vector to log item */
lv->lv_item->li_lv = lv;
/*
* If this is the first time the item is being committed to the
* CIL, store the sequence number on the log item so we can
* tell in future commits whether this is the first checkpoint
* the item is being committed into.
*/
if (!lv->lv_item->li_seq)
lv->lv_item->li_seq = log->l_cilp->xc_ctx->sequence;
}
/*
* Format log item into a flat buffers
*
* For delayed logging, we need to hold a formatted buffer containing all the
* changes on the log item. This enables us to relog the item in memory and
* write it out asynchronously without needing to relock the object that was
* modified at the time it gets written into the iclog.
*
* This function takes the prepared log vectors attached to each log item, and
* formats the changes into the log vector buffer. The buffer it uses is
* dependent on the current state of the vector in the CIL - the shadow lv is
* guaranteed to be large enough for the current modification, but we will only
* use that if we can't reuse the existing lv. If we can't reuse the existing
* lv, then simple swap it out for the shadow lv. We don't free it - that is
* done lazily either by th enext modification or the freeing of the log item.
*
* We don't set up region headers during this process; we simply copy the
* regions into the flat buffer. We can do this because we still have to do a
* formatting step to write the regions into the iclog buffer. Writing the
* ophdrs during the iclog write means that we can support splitting large
* regions across iclog boundares without needing a change in the format of the
* item/region encapsulation.
*
* Hence what we need to do now is change the rewrite the vector array to point
* to the copied region inside the buffer we just allocated. This allows us to
* format the regions into the iclog as though they are being formatted
* directly out of the objects themselves.
*/
static void
xlog_cil_insert_format_items(
struct xlog *log,
struct xfs_trans *tp,
int *diff_len)
{
struct xfs_log_item *lip;
/* Bail out if we didn't find a log item. */
if (list_empty(&tp->t_items)) {
ASSERT(0);
return;
}
list_for_each_entry(lip, &tp->t_items, li_trans) {
struct xfs_log_vec *lv;
struct xfs_log_vec *old_lv = NULL;
struct xfs_log_vec *shadow;
bool ordered = false;
/* Skip items which aren't dirty in this transaction. */
if (!test_bit(XFS_LI_DIRTY, &lip->li_flags))
continue;
/*
* The formatting size information is already attached to
* the shadow lv on the log item.
*/
shadow = lip->li_lv_shadow;
if (shadow->lv_buf_len == XFS_LOG_VEC_ORDERED)
ordered = true;
/* Skip items that do not have any vectors for writing */
if (!shadow->lv_niovecs && !ordered)
continue;
/* compare to existing item size */
old_lv = lip->li_lv;
if (lip->li_lv && shadow->lv_size <= lip->li_lv->lv_size) {
/* same or smaller, optimise common overwrite case */
lv = lip->li_lv;
if (ordered)
goto insert;
/*
* set the item up as though it is a new insertion so
* that the space reservation accounting is correct.
*/
*diff_len -= lv->lv_bytes;
/* Ensure the lv is set up according to ->iop_size */
lv->lv_niovecs = shadow->lv_niovecs;
/* reset the lv buffer information for new formatting */
lv->lv_buf_len = 0;
lv->lv_bytes = 0;
lv->lv_buf = (char *)lv +
xlog_cil_iovec_space(lv->lv_niovecs);
} else {
/* switch to shadow buffer! */
lv = shadow;
lv->lv_item = lip;
if (ordered) {
/* track as an ordered logvec */
ASSERT(lip->li_lv == NULL);
goto insert;
}
}
ASSERT(IS_ALIGNED((unsigned long)lv->lv_buf, sizeof(uint64_t)));
lip->li_ops->iop_format(lip, lv);
insert:
xfs_cil_prepare_item(log, lv, old_lv, diff_len);
}
}
/*
* The use of lockless waitqueue_active() requires that the caller has
* serialised itself against the wakeup call in xlog_cil_push_work(). That
* can be done by either holding the push lock or the context lock.
*/
static inline bool
xlog_cil_over_hard_limit(
struct xlog *log,
int32_t space_used)
{
if (waitqueue_active(&log->l_cilp->xc_push_wait))
return true;
if (space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log))
return true;
return false;
}
/*
* Insert the log items into the CIL and calculate the difference in space
* consumed by the item. Add the space to the checkpoint ticket and calculate
* if the change requires additional log metadata. If it does, take that space
* as well. Remove the amount of space we added to the checkpoint ticket from
* the current transaction ticket so that the accounting works out correctly.
*/
static void
xlog_cil_insert_items(
struct xlog *log,
struct xfs_trans *tp,
uint32_t released_space)
{
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx = cil->xc_ctx;
struct xfs_log_item *lip;
int len = 0;
int iovhdr_res = 0, split_res = 0, ctx_res = 0;
int space_used;
int order;
unsigned int cpu_nr;
struct xlog_cil_pcp *cilpcp;
ASSERT(tp);
/*
* We can do this safely because the context can't checkpoint until we
* are done so it doesn't matter exactly how we update the CIL.
*/
xlog_cil_insert_format_items(log, tp, &len);
/*
* Subtract the space released by intent cancelation from the space we
* consumed so that we remove it from the CIL space and add it back to
* the current transaction reservation context.
*/
len -= released_space;
/*
* Grab the per-cpu pointer for the CIL before we start any accounting.
* That ensures that we are running with pre-emption disabled and so we
* can't be scheduled away between split sample/update operations that
* are done without outside locking to serialise them.
*/
cpu_nr = get_cpu();
cilpcp = this_cpu_ptr(cil->xc_pcp);
/* Tell the future push that there was work added by this CPU. */
if (!cpumask_test_cpu(cpu_nr, &ctx->cil_pcpmask))
cpumask_test_and_set_cpu(cpu_nr, &ctx->cil_pcpmask);
/*
* We need to take the CIL checkpoint unit reservation on the first
* commit into the CIL. Test the XLOG_CIL_EMPTY bit first so we don't
* unnecessarily do an atomic op in the fast path here. We can clear the
* XLOG_CIL_EMPTY bit as we are under the xc_ctx_lock here and that
* needs to be held exclusively to reset the XLOG_CIL_EMPTY bit.
*/
if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags) &&
test_and_clear_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
ctx_res = ctx->ticket->t_unit_res;
/*
* Check if we need to steal iclog headers. atomic_read() is not a
* locked atomic operation, so we can check the value before we do any
* real atomic ops in the fast path. If we've already taken the CIL unit
* reservation from this commit, we've already got one iclog header
* space reserved so we have to account for that otherwise we risk
* overrunning the reservation on this ticket.
*
* If the CIL is already at the hard limit, we might need more header
* space that originally reserved. So steal more header space from every
* commit that occurs once we are over the hard limit to ensure the CIL
* push won't run out of reservation space.
*
* This can steal more than we need, but that's OK.
*
* The cil->xc_ctx_lock provides the serialisation necessary for safely
* calling xlog_cil_over_hard_limit() in this context.
*/
space_used = atomic_read(&ctx->space_used) + cilpcp->space_used + len;
if (atomic_read(&cil->xc_iclog_hdrs) > 0 ||
xlog_cil_over_hard_limit(log, space_used)) {
split_res = log->l_iclog_hsize +
sizeof(struct xlog_op_header);
if (ctx_res)
ctx_res += split_res * (tp->t_ticket->t_iclog_hdrs - 1);
else
ctx_res = split_res * tp->t_ticket->t_iclog_hdrs;
atomic_sub(tp->t_ticket->t_iclog_hdrs, &cil->xc_iclog_hdrs);
}
cilpcp->space_reserved += ctx_res;
/*
* Accurately account when over the soft limit, otherwise fold the
* percpu count into the global count if over the per-cpu threshold.
*/
if (!test_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags)) {
atomic_add(len, &ctx->space_used);
} else if (cilpcp->space_used + len >
(XLOG_CIL_SPACE_LIMIT(log) / num_online_cpus())) {
space_used = atomic_add_return(cilpcp->space_used + len,
&ctx->space_used);
cilpcp->space_used = 0;
/*
* If we just transitioned over the soft limit, we need to
* transition to the global atomic counter.
*/
if (space_used >= XLOG_CIL_SPACE_LIMIT(log))
xlog_cil_insert_pcp_aggregate(cil, ctx);
} else {
cilpcp->space_used += len;
}
/* attach the transaction to the CIL if it has any busy extents */
if (!list_empty(&tp->t_busy))
list_splice_init(&tp->t_busy, &cilpcp->busy_extents);
/*
* Now update the order of everything modified in the transaction
* and insert items into the CIL if they aren't already there.
* We do this here so we only need to take the CIL lock once during
* the transaction commit.
*/
order = atomic_inc_return(&ctx->order_id);
list_for_each_entry(lip, &tp->t_items, li_trans) {
/* Skip items which aren't dirty in this transaction. */
if (!test_bit(XFS_LI_DIRTY, &lip->li_flags))
continue;
lip->li_order_id = order;
if (!list_empty(&lip->li_cil))
continue;
list_add_tail(&lip->li_cil, &cilpcp->log_items);
}
put_cpu();
/*
* If we've overrun the reservation, dump the tx details before we move
* the log items. Shutdown is imminent...
*/
tp->t_ticket->t_curr_res -= ctx_res + len;
if (WARN_ON(tp->t_ticket->t_curr_res < 0)) {
xfs_warn(log->l_mp, "Transaction log reservation overrun:");
xfs_warn(log->l_mp,
" log items: %d bytes (iov hdrs: %d bytes)",
len, iovhdr_res);
xfs_warn(log->l_mp, " split region headers: %d bytes",
split_res);
xfs_warn(log->l_mp, " ctx ticket: %d bytes", ctx_res);
xlog_print_trans(tp);
xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
}
}
static inline void
xlog_cil_ail_insert_batch(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
struct xfs_log_item **log_items,
int nr_items,
xfs_lsn_t commit_lsn)
{
int i;
spin_lock(&ailp->ail_lock);
/* xfs_trans_ail_update_bulk drops ailp->ail_lock */
xfs_trans_ail_update_bulk(ailp, cur, log_items, nr_items, commit_lsn);
for (i = 0; i < nr_items; i++) {
struct xfs_log_item *lip = log_items[i];
if (lip->li_ops->iop_unpin)
lip->li_ops->iop_unpin(lip, 0);
}
}
/*
* Take the checkpoint's log vector chain of items and insert the attached log
* items into the AIL. This uses bulk insertion techniques to minimise AIL lock
* traffic.
*
* The AIL tracks log items via the start record LSN of the checkpoint,
* not the commit record LSN. This is because we can pipeline multiple
* checkpoints, and so the start record of checkpoint N+1 can be
* written before the commit record of checkpoint N. i.e:
*
* start N commit N
* +-------------+------------+----------------+
* start N+1 commit N+1
*
* The tail of the log cannot be moved to the LSN of commit N when all
* the items of that checkpoint are written back, because then the
* start record for N+1 is no longer in the active portion of the log
* and recovery will fail/corrupt the filesystem.
*
* Hence when all the log items in checkpoint N are written back, the
* tail of the log most now only move as far forwards as the start LSN
* of checkpoint N+1.
*
* If we are called with the aborted flag set, it is because a log write during
* a CIL checkpoint commit has failed. In this case, all the items in the
* checkpoint have already gone through iop_committed and iop_committing, which
* means that checkpoint commit abort handling is treated exactly the same as an
* iclog write error even though we haven't started any IO yet. Hence in this
* case all we need to do is iop_committed processing, followed by an
* iop_unpin(aborted) call.
*
* The AIL cursor is used to optimise the insert process. If commit_lsn is not
* at the end of the AIL, the insert cursor avoids the need to walk the AIL to
* find the insertion point on every xfs_log_item_batch_insert() call. This
* saves a lot of needless list walking and is a net win, even though it
* slightly increases that amount of AIL lock traffic to set it up and tear it
* down.
*/
static void
xlog_cil_ail_insert(
struct xfs_cil_ctx *ctx,
bool aborted)
{
#define LOG_ITEM_BATCH_SIZE 32
struct xfs_ail *ailp = ctx->cil->xc_log->l_ailp;
struct xfs_log_item *log_items[LOG_ITEM_BATCH_SIZE];
struct xfs_log_vec *lv;
struct xfs_ail_cursor cur;
xfs_lsn_t old_head;
int i = 0;
/*
* Update the AIL head LSN with the commit record LSN of this
* checkpoint. As iclogs are always completed in order, this should
* always be the same (as iclogs can contain multiple commit records) or
* higher LSN than the current head. We do this before insertion of the
* items so that log space checks during insertion will reflect the
* space that this checkpoint has already consumed. We call
* xfs_ail_update_finish() so that tail space and space-based wakeups
* will be recalculated appropriately.
*/
ASSERT(XFS_LSN_CMP(ctx->commit_lsn, ailp->ail_head_lsn) >= 0 ||
aborted);
spin_lock(&ailp->ail_lock);
xfs_trans_ail_cursor_last(ailp, &cur, ctx->start_lsn);
old_head = ailp->ail_head_lsn;
ailp->ail_head_lsn = ctx->commit_lsn;
/* xfs_ail_update_finish() drops the ail_lock */
xfs_ail_update_finish(ailp, NULLCOMMITLSN);
/*
* We move the AIL head forwards to account for the space used in the
* log before we remove that space from the grant heads. This prevents a
* transient condition where reservation space appears to become
* available on return, only for it to disappear again immediately as
* the AIL head update accounts in the log tail space.
*/
smp_wmb(); /* paired with smp_rmb in xlog_grant_space_left */
xlog_grant_return_space(ailp->ail_log, old_head, ailp->ail_head_lsn);
/* unpin all the log items */
list_for_each_entry(lv, &ctx->lv_chain, lv_list) {
struct xfs_log_item *lip = lv->lv_item;
xfs_lsn_t item_lsn;
if (aborted)
set_bit(XFS_LI_ABORTED, &lip->li_flags);
if (lip->li_ops->flags & XFS_ITEM_RELEASE_WHEN_COMMITTED) {
lip->li_ops->iop_release(lip);
continue;
}
if (lip->li_ops->iop_committed)
item_lsn = lip->li_ops->iop_committed(lip,
ctx->start_lsn);
else
item_lsn = ctx->start_lsn;
/* item_lsn of -1 means the item needs no further processing */
if (XFS_LSN_CMP(item_lsn, (xfs_lsn_t)-1) == 0)
continue;
/*
* if we are aborting the operation, no point in inserting the
* object into the AIL as we are in a shutdown situation.
*/
if (aborted) {
ASSERT(xlog_is_shutdown(ailp->ail_log));
if (lip->li_ops->iop_unpin)
lip->li_ops->iop_unpin(lip, 1);
continue;
}
if (item_lsn != ctx->start_lsn) {
/*
* Not a bulk update option due to unusual item_lsn.
* Push into AIL immediately, rechecking the lsn once
* we have the ail lock. Then unpin the item. This does
* not affect the AIL cursor the bulk insert path is
* using.
*/
spin_lock(&ailp->ail_lock);
if (XFS_LSN_CMP(item_lsn, lip->li_lsn) > 0)
xfs_trans_ail_update(ailp, lip, item_lsn);
else
spin_unlock(&ailp->ail_lock);
if (lip->li_ops->iop_unpin)
lip->li_ops->iop_unpin(lip, 0);
continue;
}
/* Item is a candidate for bulk AIL insert. */
log_items[i++] = lv->lv_item;
if (i >= LOG_ITEM_BATCH_SIZE) {
xlog_cil_ail_insert_batch(ailp, &cur, log_items,
LOG_ITEM_BATCH_SIZE, ctx->start_lsn);
i = 0;
}
}
/* make sure we insert the remainder! */
if (i)
xlog_cil_ail_insert_batch(ailp, &cur, log_items, i,
ctx->start_lsn);
spin_lock(&ailp->ail_lock);
xfs_trans_ail_cursor_done(&cur);
spin_unlock(&ailp->ail_lock);
}
static void
xlog_cil_free_logvec(
struct list_head *lv_chain)
{
struct xfs_log_vec *lv;
while (!list_empty(lv_chain)) {
lv = list_first_entry(lv_chain, struct xfs_log_vec, lv_list);
list_del_init(&lv->lv_list);
kvfree(lv);
}
}
/*
* Mark all items committed and clear busy extents. We free the log vector
* chains in a separate pass so that we unpin the log items as quickly as
* possible.
*/
static void
xlog_cil_committed(
struct xfs_cil_ctx *ctx)
{
struct xfs_mount *mp = ctx->cil->xc_log->l_mp;
bool abort = xlog_is_shutdown(ctx->cil->xc_log);
/*
* If the I/O failed, we're aborting the commit and already shutdown.
* Wake any commit waiters before aborting the log items so we don't
* block async log pushers on callbacks. Async log pushers explicitly do
* not wait on log force completion because they may be holding locks
* required to unpin items.
*/
if (abort) {
spin_lock(&ctx->cil->xc_push_lock);
wake_up_all(&ctx->cil->xc_start_wait);
wake_up_all(&ctx->cil->xc_commit_wait);
spin_unlock(&ctx->cil->xc_push_lock);
}
xlog_cil_ail_insert(ctx, abort);
xfs_extent_busy_sort(&ctx->busy_extents.extent_list);
xfs_extent_busy_clear(&ctx->busy_extents.extent_list,
xfs_has_discard(mp) && !abort);
spin_lock(&ctx->cil->xc_push_lock);
list_del(&ctx->committing);
spin_unlock(&ctx->cil->xc_push_lock);
xlog_cil_free_logvec(&ctx->lv_chain);
if (!list_empty(&ctx->busy_extents.extent_list)) {
ctx->busy_extents.owner = ctx;
xfs_discard_extents(mp, &ctx->busy_extents);
return;
}
kfree(ctx);
}
void
xlog_cil_process_committed(
struct list_head *list)
{
struct xfs_cil_ctx *ctx;
while ((ctx = list_first_entry_or_null(list,
struct xfs_cil_ctx, iclog_entry))) {
list_del(&ctx->iclog_entry);
xlog_cil_committed(ctx);
}
}
/*
* Record the LSN of the iclog we were just granted space to start writing into.
* If the context doesn't have a start_lsn recorded, then this iclog will
* contain the start record for the checkpoint. Otherwise this write contains
* the commit record for the checkpoint.
*/
void
xlog_cil_set_ctx_write_state(
struct xfs_cil_ctx *ctx,
struct xlog_in_core *iclog)
{
struct xfs_cil *cil = ctx->cil;
xfs_lsn_t lsn = be64_to_cpu(iclog->ic_header.h_lsn);
ASSERT(!ctx->commit_lsn);
if (!ctx->start_lsn) {
spin_lock(&cil->xc_push_lock);
/*
* The LSN we need to pass to the log items on transaction
* commit is the LSN reported by the first log vector write, not
* the commit lsn. If we use the commit record lsn then we can
* move the grant write head beyond the tail LSN and overwrite
* it.
*/
ctx->start_lsn = lsn;
wake_up_all(&cil->xc_start_wait);
spin_unlock(&cil->xc_push_lock);
/*
* Make sure the metadata we are about to overwrite in the log
* has been flushed to stable storage before this iclog is
* issued.
*/
spin_lock(&cil->xc_log->l_icloglock);
iclog->ic_flags |= XLOG_ICL_NEED_FLUSH;
spin_unlock(&cil->xc_log->l_icloglock);
return;
}
/*
* Take a reference to the iclog for the context so that we still hold
* it when xlog_write is done and has released it. This means the
* context controls when the iclog is released for IO.
*/
atomic_inc(&iclog->ic_refcnt);
/*
* xlog_state_get_iclog_space() guarantees there is enough space in the
* iclog for an entire commit record, so we can attach the context
* callbacks now. This needs to be done before we make the commit_lsn
* visible to waiters so that checkpoints with commit records in the
* same iclog order their IO completion callbacks in the same order that
* the commit records appear in the iclog.
*/
spin_lock(&cil->xc_log->l_icloglock);
list_add_tail(&ctx->iclog_entry, &iclog->ic_callbacks);
spin_unlock(&cil->xc_log->l_icloglock);
/*
* Now we can record the commit LSN and wake anyone waiting for this
* sequence to have the ordered commit record assigned to a physical
* location in the log.
*/
spin_lock(&cil->xc_push_lock);
ctx->commit_iclog = iclog;
ctx->commit_lsn = lsn;
wake_up_all(&cil->xc_commit_wait);
spin_unlock(&cil->xc_push_lock);
}
/*
* Ensure that the order of log writes follows checkpoint sequence order. This
* relies on the context LSN being zero until the log write has guaranteed the
* LSN that the log write will start at via xlog_state_get_iclog_space().
*/
enum _record_type {
_START_RECORD,
_COMMIT_RECORD,
};
static int
xlog_cil_order_write(
struct xfs_cil *cil,
xfs_csn_t sequence,
enum _record_type record)
{
struct xfs_cil_ctx *ctx;
restart:
spin_lock(&cil->xc_push_lock);
list_for_each_entry(ctx, &cil->xc_committing, committing) {
/*
* Avoid getting stuck in this loop because we were woken by the
* shutdown, but then went back to sleep once already in the
* shutdown state.
*/
if (xlog_is_shutdown(cil->xc_log)) {
spin_unlock(&cil->xc_push_lock);
return -EIO;
}
/*
* Higher sequences will wait for this one so skip them.
* Don't wait for our own sequence, either.
*/
if (ctx->sequence >= sequence)
continue;
/* Wait until the LSN for the record has been recorded. */
switch (record) {
case _START_RECORD:
if (!ctx->start_lsn) {
xlog_wait(&cil->xc_start_wait, &cil->xc_push_lock);
goto restart;
}
break;
case _COMMIT_RECORD:
if (!ctx->commit_lsn) {
xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
goto restart;
}
break;
}
}
spin_unlock(&cil->xc_push_lock);
return 0;
}
/*
* Write out the log vector change now attached to the CIL context. This will
* write a start record that needs to be strictly ordered in ascending CIL
* sequence order so that log recovery will always use in-order start LSNs when
* replaying checkpoints.
*/
static int
xlog_cil_write_chain(
struct xfs_cil_ctx *ctx,
uint32_t chain_len)
{
struct xlog *log = ctx->cil->xc_log;
int error;
error = xlog_cil_order_write(ctx->cil, ctx->sequence, _START_RECORD);
if (error)
return error;
return xlog_write(log, ctx, &ctx->lv_chain, ctx->ticket, chain_len);
}
/*
* Write out the commit record of a checkpoint transaction to close off a
* running log write. These commit records are strictly ordered in ascending CIL
* sequence order so that log recovery will always replay the checkpoints in the
* correct order.
*/
static int
xlog_cil_write_commit_record(
struct xfs_cil_ctx *ctx)
{
struct xlog *log = ctx->cil->xc_log;
struct xlog_op_header ophdr = {
.oh_clientid = XFS_TRANSACTION,
.oh_tid = cpu_to_be32(ctx->ticket->t_tid),
.oh_flags = XLOG_COMMIT_TRANS,
};
struct xfs_log_iovec reg = {
.i_addr = &ophdr,
.i_len = sizeof(struct xlog_op_header),
.i_type = XLOG_REG_TYPE_COMMIT,
};
struct xfs_log_vec vec = {
.lv_niovecs = 1,
.lv_iovecp = &reg,
};
int error;
LIST_HEAD(lv_chain);
list_add(&vec.lv_list, &lv_chain);
if (xlog_is_shutdown(log))
return -EIO;
error = xlog_cil_order_write(ctx->cil, ctx->sequence, _COMMIT_RECORD);
if (error)
return error;
/* account for space used by record data */
ctx->ticket->t_curr_res -= reg.i_len;
error = xlog_write(log, ctx, &lv_chain, ctx->ticket, reg.i_len);
if (error)
xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
return error;
}
struct xlog_cil_trans_hdr {
struct xlog_op_header oph[2];
struct xfs_trans_header thdr;
struct xfs_log_iovec lhdr[2];
};
/*
* Build a checkpoint transaction header to begin the journal transaction. We
* need to account for the space used by the transaction header here as it is
* not accounted for in xlog_write().
*
* This is the only place we write a transaction header, so we also build the
* log opheaders that indicate the start of a log transaction and wrap the
* transaction header. We keep the start record in it's own log vector rather
* than compacting them into a single region as this ends up making the logic
* in xlog_write() for handling empty opheaders for start, commit and unmount
* records much simpler.
*/
static void
xlog_cil_build_trans_hdr(
struct xfs_cil_ctx *ctx,
struct xlog_cil_trans_hdr *hdr,
struct xfs_log_vec *lvhdr,
int num_iovecs)
{
struct xlog_ticket *tic = ctx->ticket;
__be32 tid = cpu_to_be32(tic->t_tid);
memset(hdr, 0, sizeof(*hdr));
/* Log start record */
hdr->oph[0].oh_tid = tid;
hdr->oph[0].oh_clientid = XFS_TRANSACTION;
hdr->oph[0].oh_flags = XLOG_START_TRANS;
/* log iovec region pointer */
hdr->lhdr[0].i_addr = &hdr->oph[0];
hdr->lhdr[0].i_len = sizeof(struct xlog_op_header);
hdr->lhdr[0].i_type = XLOG_REG_TYPE_LRHEADER;
/* log opheader */
hdr->oph[1].oh_tid = tid;
hdr->oph[1].oh_clientid = XFS_TRANSACTION;
hdr->oph[1].oh_len = cpu_to_be32(sizeof(struct xfs_trans_header));
/* transaction header in host byte order format */
hdr->thdr.th_magic = XFS_TRANS_HEADER_MAGIC;
hdr->thdr.th_type = XFS_TRANS_CHECKPOINT;
hdr->thdr.th_tid = tic->t_tid;
hdr->thdr.th_num_items = num_iovecs;
/* log iovec region pointer */
hdr->lhdr[1].i_addr = &hdr->oph[1];
hdr->lhdr[1].i_len = sizeof(struct xlog_op_header) +
sizeof(struct xfs_trans_header);
hdr->lhdr[1].i_type = XLOG_REG_TYPE_TRANSHDR;
lvhdr->lv_niovecs = 2;
lvhdr->lv_iovecp = &hdr->lhdr[0];
lvhdr->lv_bytes = hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
tic->t_curr_res -= lvhdr->lv_bytes;
}
/*
* CIL item reordering compare function. We want to order in ascending ID order,
* but we want to leave items with the same ID in the order they were added to
* the list. This is important for operations like reflink where we log 4 order
* dependent intents in a single transaction when we overwrite an existing
* shared extent with a new shared extent. i.e. BUI(unmap), CUI(drop),
* CUI (inc), BUI(remap)...
*/
static int
xlog_cil_order_cmp(
void *priv,
const struct list_head *a,
const struct list_head *b)
{
struct xfs_log_vec *l1 = container_of(a, struct xfs_log_vec, lv_list);
struct xfs_log_vec *l2 = container_of(b, struct xfs_log_vec, lv_list);
return l1->lv_order_id > l2->lv_order_id;
}
/*
* Pull all the log vectors off the items in the CIL, and remove the items from
* the CIL. We don't need the CIL lock here because it's only needed on the
* transaction commit side which is currently locked out by the flush lock.
*
* If a log item is marked with a whiteout, we do not need to write it to the
* journal and so we just move them to the whiteout list for the caller to
* dispose of appropriately.
*/
static void
xlog_cil_build_lv_chain(
struct xfs_cil_ctx *ctx,
struct list_head *whiteouts,
uint32_t *num_iovecs,
uint32_t *num_bytes)
{
while (!list_empty(&ctx->log_items)) {
struct xfs_log_item *item;
struct xfs_log_vec *lv;
item = list_first_entry(&ctx->log_items,
struct xfs_log_item, li_cil);
if (test_bit(XFS_LI_WHITEOUT, &item->li_flags)) {
list_move(&item->li_cil, whiteouts);
trace_xfs_cil_whiteout_skip(item);
continue;
}
lv = item->li_lv;
lv->lv_order_id = item->li_order_id;
/* we don't write ordered log vectors */
if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
*num_bytes += lv->lv_bytes;
*num_iovecs += lv->lv_niovecs;
list_add_tail(&lv->lv_list, &ctx->lv_chain);
list_del_init(&item->li_cil);
item->li_order_id = 0;
item->li_lv = NULL;
}
}
static void
xlog_cil_cleanup_whiteouts(
struct list_head *whiteouts)
{
while (!list_empty(whiteouts)) {
struct xfs_log_item *item = list_first_entry(whiteouts,
struct xfs_log_item, li_cil);
list_del_init(&item->li_cil);
trace_xfs_cil_whiteout_unpin(item);
item->li_ops->iop_unpin(item, 1);
}
}
/*
* Push the Committed Item List to the log.
*
* If the current sequence is the same as xc_push_seq we need to do a flush. If
* xc_push_seq is less than the current sequence, then it has already been
* flushed and we don't need to do anything - the caller will wait for it to
* complete if necessary.
*
* xc_push_seq is checked unlocked against the sequence number for a match.
* Hence we can allow log forces to run racily and not issue pushes for the
* same sequence twice. If we get a race between multiple pushes for the same
* sequence they will block on the first one and then abort, hence avoiding
* needless pushes.
*
* This runs from a workqueue so it does not inherent any specific memory
* allocation context. However, we do not want to block on memory reclaim
* recursing back into the filesystem because this push may have been triggered
* by memory reclaim itself. Hence we really need to run under full GFP_NOFS
* contraints here.
*/
static void
xlog_cil_push_work(
struct work_struct *work)
{
unsigned int nofs_flags = memalloc_nofs_save();
struct xfs_cil_ctx *ctx =
container_of(work, struct xfs_cil_ctx, push_work);
struct xfs_cil *cil = ctx->cil;
struct xlog *log = cil->xc_log;
struct xfs_cil_ctx *new_ctx;
int num_iovecs = 0;
int num_bytes = 0;
int error = 0;
struct xlog_cil_trans_hdr thdr;
struct xfs_log_vec lvhdr = {};
xfs_csn_t push_seq;
bool push_commit_stable;
LIST_HEAD (whiteouts);
struct xlog_ticket *ticket;
new_ctx = xlog_cil_ctx_alloc();
new_ctx->ticket = xlog_cil_ticket_alloc(log);
down_write(&cil->xc_ctx_lock);
spin_lock(&cil->xc_push_lock);
push_seq = cil->xc_push_seq;
ASSERT(push_seq <= ctx->sequence);
push_commit_stable = cil->xc_push_commit_stable;
cil->xc_push_commit_stable = false;
/*
* As we are about to switch to a new, empty CIL context, we no longer
* need to throttle tasks on CIL space overruns. Wake any waiters that
* the hard push throttle may have caught so they can start committing
* to the new context. The ctx->xc_push_lock provides the serialisation
* necessary for safely using the lockless waitqueue_active() check in
* this context.
*/
if (waitqueue_active(&cil->xc_push_wait))
wake_up_all(&cil->xc_push_wait);
xlog_cil_push_pcp_aggregate(cil, ctx);
/*
* Check if we've anything to push. If there is nothing, then we don't
* move on to a new sequence number and so we have to be able to push
* this sequence again later.
*/
if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags)) {
cil->xc_push_seq = 0;
spin_unlock(&cil->xc_push_lock);
goto out_skip;
}
/* check for a previously pushed sequence */
if (push_seq < ctx->sequence) {
spin_unlock(&cil->xc_push_lock);
goto out_skip;
}
/*
* We are now going to push this context, so add it to the committing
* list before we do anything else. This ensures that anyone waiting on
* this push can easily detect the difference between a "push in
* progress" and "CIL is empty, nothing to do".
*
* IOWs, a wait loop can now check for:
* the current sequence not being found on the committing list;
* an empty CIL; and
* an unchanged sequence number
* to detect a push that had nothing to do and therefore does not need
* waiting on. If the CIL is not empty, we get put on the committing
* list before emptying the CIL and bumping the sequence number. Hence
* an empty CIL and an unchanged sequence number means we jumped out
* above after doing nothing.
*
* Hence the waiter will either find the commit sequence on the
* committing list or the sequence number will be unchanged and the CIL
* still dirty. In that latter case, the push has not yet started, and
* so the waiter will have to continue trying to check the CIL
* committing list until it is found. In extreme cases of delay, the
* sequence may fully commit between the attempts the wait makes to wait
* on the commit sequence.
*/
list_add(&ctx->committing, &cil->xc_committing);
spin_unlock(&cil->xc_push_lock);
xlog_cil_build_lv_chain(ctx, &whiteouts, &num_iovecs, &num_bytes);
/*
* Switch the contexts so we can drop the context lock and move out
* of a shared context. We can't just go straight to the commit record,
* though - we need to synchronise with previous and future commits so
* that the commit records are correctly ordered in the log to ensure
* that we process items during log IO completion in the correct order.
*
* For example, if we get an EFI in one checkpoint and the EFD in the
* next (e.g. due to log forces), we do not want the checkpoint with
* the EFD to be committed before the checkpoint with the EFI. Hence
* we must strictly order the commit records of the checkpoints so
* that: a) the checkpoint callbacks are attached to the iclogs in the
* correct order; and b) the checkpoints are replayed in correct order
* in log recovery.
*
* Hence we need to add this context to the committing context list so
* that higher sequences will wait for us to write out a commit record
* before they do.
*
* xfs_log_force_seq requires us to mirror the new sequence into the cil
* structure atomically with the addition of this sequence to the
* committing list. This also ensures that we can do unlocked checks
* against the current sequence in log forces without risking
* deferencing a freed context pointer.
*/
spin_lock(&cil->xc_push_lock);
xlog_cil_ctx_switch(cil, new_ctx);
spin_unlock(&cil->xc_push_lock);
up_write(&cil->xc_ctx_lock);
/*
* Sort the log vector chain before we add the transaction headers.
* This ensures we always have the transaction headers at the start
* of the chain.
*/
list_sort(NULL, &ctx->lv_chain, xlog_cil_order_cmp);
/*
* Build a checkpoint transaction header and write it to the log to
* begin the transaction. We need to account for the space used by the
* transaction header here as it is not accounted for in xlog_write().
* Add the lvhdr to the head of the lv chain we pass to xlog_write() so
* it gets written into the iclog first.
*/
xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
num_bytes += lvhdr.lv_bytes;
list_add(&lvhdr.lv_list, &ctx->lv_chain);
/*
* Take the lvhdr back off the lv_chain immediately after calling
* xlog_cil_write_chain() as it should not be passed to log IO
* completion.
*/
error = xlog_cil_write_chain(ctx, num_bytes);
list_del(&lvhdr.lv_list);
if (error)
goto out_abort_free_ticket;
error = xlog_cil_write_commit_record(ctx);
if (error)
goto out_abort_free_ticket;
/*
* Grab the ticket from the ctx so we can ungrant it after releasing the
* commit_iclog. The ctx may be freed by the time we return from
* releasing the commit_iclog (i.e. checkpoint has been completed and
* callback run) so we can't reference the ctx after the call to
* xlog_state_release_iclog().
*/
ticket = ctx->ticket;
/*
* If the checkpoint spans multiple iclogs, wait for all previous iclogs
* to complete before we submit the commit_iclog. We can't use state
* checks for this - ACTIVE can be either a past completed iclog or a
* future iclog being filled, while WANT_SYNC through SYNC_DONE can be a
* past or future iclog awaiting IO or ordered IO completion to be run.
* In the latter case, if it's a future iclog and we wait on it, the we
* will hang because it won't get processed through to ic_force_wait
* wakeup until this commit_iclog is written to disk. Hence we use the
* iclog header lsn and compare it to the commit lsn to determine if we
* need to wait on iclogs or not.
*/
spin_lock(&log->l_icloglock);
if (ctx->start_lsn != ctx->commit_lsn) {
xfs_lsn_t plsn;
plsn = be64_to_cpu(ctx->commit_iclog->ic_prev->ic_header.h_lsn);
if (plsn && XFS_LSN_CMP(plsn, ctx->commit_lsn) < 0) {
/*
* Waiting on ic_force_wait orders the completion of
* iclogs older than ic_prev. Hence we only need to wait
* on the most recent older iclog here.
*/
xlog_wait_on_iclog(ctx->commit_iclog->ic_prev);
spin_lock(&log->l_icloglock);
}
/*
* We need to issue a pre-flush so that the ordering for this
* checkpoint is correctly preserved down to stable storage.
*/
ctx->commit_iclog->ic_flags |= XLOG_ICL_NEED_FLUSH;
}
/*
* The commit iclog must be written to stable storage to guarantee
* journal IO vs metadata writeback IO is correctly ordered on stable
* storage.
*
* If the push caller needs the commit to be immediately stable and the
* commit_iclog is not yet marked as XLOG_STATE_WANT_SYNC to indicate it
* will be written when released, switch it's state to WANT_SYNC right
* now.
*/
ctx->commit_iclog->ic_flags |= XLOG_ICL_NEED_FUA;
if (push_commit_stable &&
ctx->commit_iclog->ic_state == XLOG_STATE_ACTIVE)
xlog_state_switch_iclogs(log, ctx->commit_iclog, 0);
ticket = ctx->ticket;
xlog_state_release_iclog(log, ctx->commit_iclog, ticket);
/* Not safe to reference ctx now! */
spin_unlock(&log->l_icloglock);
xlog_cil_cleanup_whiteouts(&whiteouts);
xfs_log_ticket_ungrant(log, ticket);
memalloc_nofs_restore(nofs_flags);
return;
out_skip:
up_write(&cil->xc_ctx_lock);
xfs_log_ticket_put(new_ctx->ticket);
kfree(new_ctx);
memalloc_nofs_restore(nofs_flags);
return;
out_abort_free_ticket:
ASSERT(xlog_is_shutdown(log));
xlog_cil_cleanup_whiteouts(&whiteouts);
if (!ctx->commit_iclog) {
xfs_log_ticket_ungrant(log, ctx->ticket);
xlog_cil_committed(ctx);
memalloc_nofs_restore(nofs_flags);
return;
}
spin_lock(&log->l_icloglock);
ticket = ctx->ticket;
xlog_state_release_iclog(log, ctx->commit_iclog, ticket);
/* Not safe to reference ctx now! */
spin_unlock(&log->l_icloglock);
xfs_log_ticket_ungrant(log, ticket);
memalloc_nofs_restore(nofs_flags);
}
/*
* We need to push CIL every so often so we don't cache more than we can fit in
* the log. The limit really is that a checkpoint can't be more than half the
* log (the current checkpoint is not allowed to overwrite the previous
* checkpoint), but commit latency and memory usage limit this to a smaller
* size.
*/
static void
xlog_cil_push_background(
struct xlog *log)
{
struct xfs_cil *cil = log->l_cilp;
int space_used = atomic_read(&cil->xc_ctx->space_used);
/*
* The cil won't be empty because we are called while holding the
* context lock so whatever we added to the CIL will still be there.
*/
ASSERT(!test_bit(XLOG_CIL_EMPTY, &cil->xc_flags));
/*
* We are done if:
* - we haven't used up all the space available yet; or
* - we've already queued up a push; and
* - we're not over the hard limit; and
* - nothing has been over the hard limit.
*
* If so, we don't need to take the push lock as there's nothing to do.
*/
if (space_used < XLOG_CIL_SPACE_LIMIT(log) ||
(cil->xc_push_seq == cil->xc_current_sequence &&
space_used < XLOG_CIL_BLOCKING_SPACE_LIMIT(log) &&
!waitqueue_active(&cil->xc_push_wait))) {
up_read(&cil->xc_ctx_lock);
return;
}
spin_lock(&cil->xc_push_lock);
if (cil->xc_push_seq < cil->xc_current_sequence) {
cil->xc_push_seq = cil->xc_current_sequence;
queue_work(cil->xc_push_wq, &cil->xc_ctx->push_work);
}
/*
* Drop the context lock now, we can't hold that if we need to sleep
* because we are over the blocking threshold. The push_lock is still
* held, so blocking threshold sleep/wakeup is still correctly
* serialised here.
*/
up_read(&cil->xc_ctx_lock);
/*
* If we are well over the space limit, throttle the work that is being
* done until the push work on this context has begun. Enforce the hard
* throttle on all transaction commits once it has been activated, even
* if the committing transactions have resulted in the space usage
* dipping back down under the hard limit.
*
* The ctx->xc_push_lock provides the serialisation necessary for safely
* calling xlog_cil_over_hard_limit() in this context.
*/
if (xlog_cil_over_hard_limit(log, space_used)) {
trace_xfs_log_cil_wait(log, cil->xc_ctx->ticket);
ASSERT(space_used < log->l_logsize);
xlog_wait(&cil->xc_push_wait, &cil->xc_push_lock);
return;
}
spin_unlock(&cil->xc_push_lock);
}
/*
* xlog_cil_push_now() is used to trigger an immediate CIL push to the sequence
* number that is passed. When it returns, the work will be queued for
* @push_seq, but it won't be completed.
*
* If the caller is performing a synchronous force, we will flush the workqueue
* to get previously queued work moving to minimise the wait time they will
* undergo waiting for all outstanding pushes to complete. The caller is
* expected to do the required waiting for push_seq to complete.
*
* If the caller is performing an async push, we need to ensure that the
* checkpoint is fully flushed out of the iclogs when we finish the push. If we
* don't do this, then the commit record may remain sitting in memory in an
* ACTIVE iclog. This then requires another full log force to push to disk,
* which defeats the purpose of having an async, non-blocking CIL force
* mechanism. Hence in this case we need to pass a flag to the push work to
* indicate it needs to flush the commit record itself.
*/
static void
xlog_cil_push_now(
struct xlog *log,
xfs_lsn_t push_seq,
bool async)
{
struct xfs_cil *cil = log->l_cilp;
if (!cil)
return;
ASSERT(push_seq && push_seq <= cil->xc_current_sequence);
/* start on any pending background push to minimise wait time on it */
if (!async)
flush_workqueue(cil->xc_push_wq);
spin_lock(&cil->xc_push_lock);
/*
* If this is an async flush request, we always need to set the
* xc_push_commit_stable flag even if something else has already queued
* a push. The flush caller is asking for the CIL to be on stable
* storage when the next push completes, so regardless of who has queued
* the push, the flush requires stable semantics from it.
*/
cil->xc_push_commit_stable = async;
/*
* If the CIL is empty or we've already pushed the sequence then
* there's no more work that we need to do.
*/
if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags) ||
push_seq <= cil->xc_push_seq) {
spin_unlock(&cil->xc_push_lock);
return;
}
cil->xc_push_seq = push_seq;
queue_work(cil->xc_push_wq, &cil->xc_ctx->push_work);
spin_unlock(&cil->xc_push_lock);
}
bool
xlog_cil_empty(
struct xlog *log)
{
struct xfs_cil *cil = log->l_cilp;
bool empty = false;
spin_lock(&cil->xc_push_lock);
if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
empty = true;
spin_unlock(&cil->xc_push_lock);
return empty;
}
/*
* If there are intent done items in this transaction and the related intent was
* committed in the current (same) CIL checkpoint, we don't need to write either
* the intent or intent done item to the journal as the change will be
* journalled atomically within this checkpoint. As we cannot remove items from
* the CIL here, mark the related intent with a whiteout so that the CIL push
* can remove it rather than writing it to the journal. Then remove the intent
* done item from the current transaction and release it so it doesn't get put
* into the CIL at all.
*/
static uint32_t
xlog_cil_process_intents(
struct xfs_cil *cil,
struct xfs_trans *tp)
{
struct xfs_log_item *lip, *ilip, *next;
uint32_t len = 0;
list_for_each_entry_safe(lip, next, &tp->t_items, li_trans) {
if (!(lip->li_ops->flags & XFS_ITEM_INTENT_DONE))
continue;
ilip = lip->li_ops->iop_intent(lip);
if (!ilip || !xlog_item_in_current_chkpt(cil, ilip))
continue;
set_bit(XFS_LI_WHITEOUT, &ilip->li_flags);
trace_xfs_cil_whiteout_mark(ilip);
len += ilip->li_lv->lv_bytes;
kvfree(ilip->li_lv);
ilip->li_lv = NULL;
xfs_trans_del_item(lip);
lip->li_ops->iop_release(lip);
}
return len;
}
/*
* Commit a transaction with the given vector to the Committed Item List.
*
* To do this, we need to format the item, pin it in memory if required and
* account for the space used by the transaction. Once we have done that we
* need to release the unused reservation for the transaction, attach the
* transaction to the checkpoint context so we carry the busy extents through
* to checkpoint completion, and then unlock all the items in the transaction.
*
* Called with the context lock already held in read mode to lock out
* background commit, returns without it held once background commits are
* allowed again.
*/
void
xlog_cil_commit(
struct xlog *log,
struct xfs_trans *tp,
xfs_csn_t *commit_seq,
bool regrant)
{
struct xfs_cil *cil = log->l_cilp;
struct xfs_log_item *lip, *next;
uint32_t released_space = 0;
/*
* Do all necessary memory allocation before we lock the CIL.
* This ensures the allocation does not deadlock with a CIL
* push in memory reclaim (e.g. from kswapd).
*/
xlog_cil_alloc_shadow_bufs(log, tp);
/* lock out background commit */
down_read(&cil->xc_ctx_lock);
if (tp->t_flags & XFS_TRANS_HAS_INTENT_DONE)
released_space = xlog_cil_process_intents(cil, tp);
xlog_cil_insert_items(log, tp, released_space);
if (regrant && !xlog_is_shutdown(log))
xfs_log_ticket_regrant(log, tp->t_ticket);
else
xfs_log_ticket_ungrant(log, tp->t_ticket);
tp->t_ticket = NULL;
xfs_trans_unreserve_and_mod_sb(tp);
/*
* Once all the items of the transaction have been copied to the CIL,
* the items can be unlocked and possibly freed.
*
* This needs to be done before we drop the CIL context lock because we
* have to update state in the log items and unlock them before they go
* to disk. If we don't, then the CIL checkpoint can race with us and
* we can run checkpoint completion before we've updated and unlocked
* the log items. This affects (at least) processing of stale buffers,
* inodes and EFIs.
*/
trace_xfs_trans_commit_items(tp, _RET_IP_);
list_for_each_entry_safe(lip, next, &tp->t_items, li_trans) {
xfs_trans_del_item(lip);
if (lip->li_ops->iop_committing)
lip->li_ops->iop_committing(lip, cil->xc_ctx->sequence);
}
if (commit_seq)
*commit_seq = cil->xc_ctx->sequence;
/* xlog_cil_push_background() releases cil->xc_ctx_lock */
xlog_cil_push_background(log);
}
/*
* Flush the CIL to stable storage but don't wait for it to complete. This
* requires the CIL push to ensure the commit record for the push hits the disk,
* but otherwise is no different to a push done from a log force.
*/
void
xlog_cil_flush(
struct xlog *log)
{
xfs_csn_t seq = log->l_cilp->xc_current_sequence;
trace_xfs_log_force(log->l_mp, seq, _RET_IP_);
xlog_cil_push_now(log, seq, true);
/*
* If the CIL is empty, make sure that any previous checkpoint that may
* still be in an active iclog is pushed to stable storage.
*/
if (test_bit(XLOG_CIL_EMPTY, &log->l_cilp->xc_flags))
xfs_log_force(log->l_mp, 0);
}
/*
* Conditionally push the CIL based on the sequence passed in.
*
* We only need to push if we haven't already pushed the sequence number given.
* Hence the only time we will trigger a push here is if the push sequence is
* the same as the current context.
*
* We return the current commit lsn to allow the callers to determine if a
* iclog flush is necessary following this call.
*/
xfs_lsn_t
xlog_cil_force_seq(
struct xlog *log,
xfs_csn_t sequence)
{
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx;
xfs_lsn_t commit_lsn = NULLCOMMITLSN;
ASSERT(sequence <= cil->xc_current_sequence);
if (!sequence)
sequence = cil->xc_current_sequence;
trace_xfs_log_force(log->l_mp, sequence, _RET_IP_);
/*
* check to see if we need to force out the current context.
* xlog_cil_push() handles racing pushes for the same sequence,
* so no need to deal with it here.
*/
restart:
xlog_cil_push_now(log, sequence, false);
/*
* See if we can find a previous sequence still committing.
* We need to wait for all previous sequence commits to complete
* before allowing the force of push_seq to go ahead. Hence block
* on commits for those as well.
*/
spin_lock(&cil->xc_push_lock);
list_for_each_entry(ctx, &cil->xc_committing, committing) {
/*
* Avoid getting stuck in this loop because we were woken by the
* shutdown, but then went back to sleep once already in the
* shutdown state.
*/
if (xlog_is_shutdown(log))
goto out_shutdown;
if (ctx->sequence > sequence)
continue;
if (!ctx->commit_lsn) {
/*
* It is still being pushed! Wait for the push to
* complete, then start again from the beginning.
*/
XFS_STATS_INC(log->l_mp, xs_log_force_sleep);
xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
goto restart;
}
if (ctx->sequence != sequence)
continue;
/* found it! */
commit_lsn = ctx->commit_lsn;
}
/*
* The call to xlog_cil_push_now() executes the push in the background.
* Hence by the time we have got here it our sequence may not have been
* pushed yet. This is true if the current sequence still matches the
* push sequence after the above wait loop and the CIL still contains
* dirty objects. This is guaranteed by the push code first adding the
* context to the committing list before emptying the CIL.
*
* Hence if we don't find the context in the committing list and the
* current sequence number is unchanged then the CIL contents are
* significant. If the CIL is empty, if means there was nothing to push
* and that means there is nothing to wait for. If the CIL is not empty,
* it means we haven't yet started the push, because if it had started
* we would have found the context on the committing list.
*/
if (sequence == cil->xc_current_sequence &&
!test_bit(XLOG_CIL_EMPTY, &cil->xc_flags)) {
spin_unlock(&cil->xc_push_lock);
goto restart;
}
spin_unlock(&cil->xc_push_lock);
return commit_lsn;
/*
* We detected a shutdown in progress. We need to trigger the log force
* to pass through it's iclog state machine error handling, even though
* we are already in a shutdown state. Hence we can't return
* NULLCOMMITLSN here as that has special meaning to log forces (i.e.
* LSN is already stable), so we return a zero LSN instead.
*/
out_shutdown:
spin_unlock(&cil->xc_push_lock);
return 0;
}
/*
* Perform initial CIL structure initialisation.
*/
int
xlog_cil_init(
struct xlog *log)
{
struct xfs_cil *cil;
struct xfs_cil_ctx *ctx;
struct xlog_cil_pcp *cilpcp;
int cpu;
cil = kzalloc(sizeof(*cil), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
if (!cil)
return -ENOMEM;
/*
* Limit the CIL pipeline depth to 4 concurrent works to bound the
* concurrency the log spinlocks will be exposed to.
*/
cil->xc_push_wq = alloc_workqueue("xfs-cil/%s",
XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_UNBOUND),
4, log->l_mp->m_super->s_id);
if (!cil->xc_push_wq)
goto out_destroy_cil;
cil->xc_log = log;
cil->xc_pcp = alloc_percpu(struct xlog_cil_pcp);
if (!cil->xc_pcp)
goto out_destroy_wq;
for_each_possible_cpu(cpu) {
cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
INIT_LIST_HEAD(&cilpcp->busy_extents);
INIT_LIST_HEAD(&cilpcp->log_items);
}
INIT_LIST_HEAD(&cil->xc_committing);
spin_lock_init(&cil->xc_push_lock);
init_waitqueue_head(&cil->xc_push_wait);
init_rwsem(&cil->xc_ctx_lock);
init_waitqueue_head(&cil->xc_start_wait);
init_waitqueue_head(&cil->xc_commit_wait);
log->l_cilp = cil;
ctx = xlog_cil_ctx_alloc();
xlog_cil_ctx_switch(cil, ctx);
return 0;
out_destroy_wq:
destroy_workqueue(cil->xc_push_wq);
out_destroy_cil:
kfree(cil);
return -ENOMEM;
}
void
xlog_cil_destroy(
struct xlog *log)
{
struct xfs_cil *cil = log->l_cilp;
if (cil->xc_ctx) {
if (cil->xc_ctx->ticket)
xfs_log_ticket_put(cil->xc_ctx->ticket);
kfree(cil->xc_ctx);
}
ASSERT(test_bit(XLOG_CIL_EMPTY, &cil->xc_flags));
free_percpu(cil->xc_pcp);
destroy_workqueue(cil->xc_push_wq);
kfree(cil);
}