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afs: Don't use folio->private to record partial modification

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AFS currently uses folio->private to store the range of bytes within a
folio that have been modified - the idea being that if we have, say, a 2MiB
folio and someone writes a single byte, we only have to write back that
single page and not the whole 2MiB folio - thereby saving on network
bandwidth.

Remove this, at least for now, and accept the extra network load (which
doesn't matter in the common case of writing a whole file at a time from
beginning to end).

This makes folio->private available for netfslib to use.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
This commit is contained in:
David Howells 2022-12-02 14:12:41 +00:00
parent 5f5ce7ba15
commit a34847d4b7
4 changed files with 43 additions and 286 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
fs/afs/file.c
View File

@ -386,63 +386,6 @@ const struct netfs_request_ops afs_req_ops = {
.issue_read = afs_issue_read,
};
/*
* Adjust the dirty region of the page on truncation or full invalidation,
* getting rid of the markers altogether if the region is entirely invalidated.
*/
static void afs_invalidate_dirty(struct folio *folio, size_t offset,
size_t length)
{
struct afs_vnode *vnode = AFS_FS_I(folio_inode(folio));
unsigned long priv;
unsigned int f, t, end = offset + length;
priv = (unsigned long)folio_get_private(folio);
/* we clean up only if the entire page is being invalidated */
if (offset == 0 && length == folio_size(folio))
goto full_invalidate;
/* If the page was dirtied by page_mkwrite(), the PTE stays writable
* and we don't get another notification to tell us to expand it
* again.
*/
if (afs_is_folio_dirty_mmapped(priv))
return;
/* We may need to shorten the dirty region */
f = afs_folio_dirty_from(folio, priv);
t = afs_folio_dirty_to(folio, priv);
if (t <= offset || f >= end)
return; /* Doesn't overlap */
if (f < offset && t > end)
return; /* Splits the dirty region - just absorb it */
if (f >= offset && t <= end)
goto undirty;
if (f < offset)
t = offset;
else
f = end;
if (f == t)
goto undirty;
priv = afs_folio_dirty(folio, f, t);
folio_change_private(folio, (void *)priv);
trace_afs_folio_dirty(vnode, tracepoint_string("trunc"), folio);
return;
undirty:
trace_afs_folio_dirty(vnode, tracepoint_string("undirty"), folio);
folio_clear_dirty_for_io(folio);
full_invalidate:
trace_afs_folio_dirty(vnode, tracepoint_string("inval"), folio);
folio_detach_private(folio);
}
/*
* invalidate part or all of a page
* - release a page and clean up its private data if offset is 0 (indicating
@ -453,11 +396,6 @@ static void afs_invalidate_folio(struct folio *folio, size_t offset,
{
_enter("{%lu},%zu,%zu", folio->index, offset, length);
BUG_ON(!folio_test_locked(folio));
if (folio_get_private(folio))
afs_invalidate_dirty(folio, offset, length);
folio_wait_fscache(folio);
_leave("");
}
@ -485,11 +423,6 @@ static bool afs_release_folio(struct folio *folio, gfp_t gfp)
fscache_note_page_release(afs_vnode_cache(vnode));
#endif
if (folio_test_private(folio)) {
trace_afs_folio_dirty(vnode, tracepoint_string("rel"), folio);
folio_detach_private(folio);
}
/* Indicate that the folio can be released */
_leave(" = T");
return true;

56
fs/afs/internal.h
View File

@ -894,62 +894,6 @@ static inline void afs_invalidate_cache(struct afs_vnode *vnode, unsigned int fl
i_size_read(&vnode->netfs.inode), flags);
}
/*
* We use folio->private to hold the amount of the folio that we've written to,
* splitting the field into two parts. However, we need to represent a range
* 0...FOLIO_SIZE, so we reduce the resolution if the size of the folio
* exceeds what we can encode.
*/
#ifdef CONFIG_64BIT
#define __AFS_FOLIO_PRIV_MASK 0x7fffffffUL
#define __AFS_FOLIO_PRIV_SHIFT 32
#define __AFS_FOLIO_PRIV_MMAPPED 0x80000000UL
#else
#define __AFS_FOLIO_PRIV_MASK 0x7fffUL
#define __AFS_FOLIO_PRIV_SHIFT 16
#define __AFS_FOLIO_PRIV_MMAPPED 0x8000UL
#endif
static inline unsigned int afs_folio_dirty_resolution(struct folio *folio)
{
int shift = folio_shift(folio) - (__AFS_FOLIO_PRIV_SHIFT - 1);
return (shift > 0) ? shift : 0;
}
static inline size_t afs_folio_dirty_from(struct folio *folio, unsigned long priv)
{
unsigned long x = priv & __AFS_FOLIO_PRIV_MASK;
/* The lower bound is inclusive */
return x << afs_folio_dirty_resolution(folio);
}
static inline size_t afs_folio_dirty_to(struct folio *folio, unsigned long priv)
{
unsigned long x = (priv >> __AFS_FOLIO_PRIV_SHIFT) & __AFS_FOLIO_PRIV_MASK;
/* The upper bound is immediately beyond the region */
return (x + 1) << afs_folio_dirty_resolution(folio);
}
static inline unsigned long afs_folio_dirty(struct folio *folio, size_t from, size_t to)
{
unsigned int res = afs_folio_dirty_resolution(folio);
from >>= res;
to = (to - 1) >> res;
return (to << __AFS_FOLIO_PRIV_SHIFT) | from;
}
static inline unsigned long afs_folio_dirty_mmapped(unsigned long priv)
{
return priv | __AFS_FOLIO_PRIV_MMAPPED;
}
static inline bool afs_is_folio_dirty_mmapped(unsigned long priv)
{
return priv & __AFS_FOLIO_PRIV_MMAPPED;
}
#include <trace/events/afs.h>
/*****************************************************************************/

190
fs/afs/write.c
View File

@ -16,7 +16,8 @@
static int afs_writepages_region(struct address_space *mapping,
struct writeback_control *wbc,
loff_t start, loff_t end, loff_t *_next,
unsigned long long start,
unsigned long long end, loff_t *_next,
bool max_one_loop);
static void afs_write_to_cache(struct afs_vnode *vnode, loff_t start, size_t len,
@ -34,25 +35,6 @@ static void afs_folio_start_fscache(bool caching, struct folio *folio)
}
#endif
/*
* Flush out a conflicting write. This may extend the write to the surrounding
* pages if also dirty and contiguous to the conflicting region..
*/
static int afs_flush_conflicting_write(struct address_space *mapping,
struct folio *folio)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_ALL,
.nr_to_write = LONG_MAX,
.range_start = folio_pos(folio),
.range_end = LLONG_MAX,
};
loff_t next;
return afs_writepages_region(mapping, &wbc, folio_pos(folio), LLONG_MAX,
&next, true);
}
/*
* prepare to perform part of a write to a page
*/
@ -62,10 +44,6 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
struct folio *folio;
unsigned long priv;
unsigned f, from;
unsigned t, to;
pgoff_t index;
int ret;
_enter("{%llx:%llu},%llx,%x",
@ -79,49 +57,20 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
if (ret < 0)
return ret;
index = folio_index(folio);
from = pos - index * PAGE_SIZE;
to = from + len;
try_again:
/* See if this page is already partially written in a way that we can
* merge the new write with.
*/
if (folio_test_private(folio)) {
priv = (unsigned long)folio_get_private(folio);
f = afs_folio_dirty_from(folio, priv);
t = afs_folio_dirty_to(folio, priv);
ASSERTCMP(f, <=, t);
if (folio_test_writeback(folio)) {
trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
folio_unlock(folio);
goto wait_for_writeback;
}
/* If the file is being filled locally, allow inter-write
* spaces to be merged into writes. If it's not, only write
* back what the user gives us.
*/
if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
(to < f || from > t))
goto flush_conflicting_write;
if (folio_test_writeback(folio)) {
trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
folio_unlock(folio);
goto wait_for_writeback;
}
*_page = folio_file_page(folio, pos / PAGE_SIZE);
_leave(" = 0");
return 0;
/* The previous write and this write aren't adjacent or overlapping, so
* flush the page out.
*/
flush_conflicting_write:
trace_afs_folio_dirty(vnode, tracepoint_string("confl"), folio);
folio_unlock(folio);
ret = afs_flush_conflicting_write(mapping, folio);
if (ret < 0)
goto error;
wait_for_writeback:
ret = folio_wait_writeback_killable(folio);
if (ret < 0)
@ -147,9 +96,6 @@ int afs_write_end(struct file *file, struct address_space *mapping,
{
struct folio *folio = page_folio(subpage);
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
unsigned long priv;
unsigned int f, from = offset_in_folio(folio, pos);
unsigned int t, to = from + copied;
loff_t i_size, write_end_pos;
_enter("{%llx:%llu},{%lx}",
@ -179,23 +125,6 @@ int afs_write_end(struct file *file, struct address_space *mapping,
fscache_update_cookie(afs_vnode_cache(vnode), NULL, &write_end_pos);
}
if (folio_test_private(folio)) {
priv = (unsigned long)folio_get_private(folio);
f = afs_folio_dirty_from(folio, priv);
t = afs_folio_dirty_to(folio, priv);
if (from < f)
f = from;
if (to > t)
t = to;
priv = afs_folio_dirty(folio, f, t);
folio_change_private(folio, (void *)priv);
trace_afs_folio_dirty(vnode, tracepoint_string("dirty+"), folio);
} else {
priv = afs_folio_dirty(folio, from, to);
folio_attach_private(folio, (void *)priv);
trace_afs_folio_dirty(vnode, tracepoint_string("dirty"), folio);
}
if (folio_mark_dirty(folio))
_debug("dirtied %lx", folio_index(folio));
@ -300,7 +229,6 @@ static void afs_pages_written_back(struct afs_vnode *vnode, loff_t start, unsign
}
trace_afs_folio_dirty(vnode, tracepoint_string("clear"), folio);
folio_detach_private(folio);
folio_end_writeback(folio);
}
@ -454,17 +382,12 @@ static void afs_extend_writeback(struct address_space *mapping,
long *_count,
loff_t start,
loff_t max_len,
bool new_content,
bool caching,
unsigned int *_len)
size_t *_len)
{
struct folio_batch fbatch;
struct folio *folio;
unsigned long priv;
unsigned int psize, filler = 0;
unsigned int f, t;
loff_t len = *_len;
pgoff_t index = (start + len) / PAGE_SIZE;
pgoff_t index = (start + *_len) / PAGE_SIZE;
bool stop = true;
unsigned int i;
@ -492,7 +415,7 @@ static void afs_extend_writeback(struct address_space *mapping,
continue;
}
/* Has the page moved or been split? */
/* Has the folio moved or been split? */
if (unlikely(folio != xas_reload(&xas))) {
folio_put(folio);
break;
@ -510,24 +433,13 @@ static void afs_extend_writeback(struct address_space *mapping,
break;
}
psize = folio_size(folio);
priv = (unsigned long)folio_get_private(folio);
f = afs_folio_dirty_from(folio, priv);
t = afs_folio_dirty_to(folio, priv);
if (f != 0 && !new_content) {
folio_unlock(folio);
folio_put(folio);
break;
}
len += filler + t;
filler = psize - t;
if (len >= max_len || *_count <= 0)
stop = true;
else if (t == psize || new_content)
stop = false;
index += folio_nr_pages(folio);
*_count -= folio_nr_pages(folio);
*_len += folio_size(folio);
stop = false;
if (*_len >= max_len || *_count <= 0)
stop = true;
if (!folio_batch_add(&fbatch, folio))
break;
if (stop)
@ -553,16 +465,12 @@ static void afs_extend_writeback(struct address_space *mapping,
if (folio_start_writeback(folio))
BUG();
afs_folio_start_fscache(caching, folio);
*_count -= folio_nr_pages(folio);
folio_unlock(folio);
}
folio_batch_release(&fbatch);
cond_resched();
} while (!stop);
*_len = len;
}
/*
@ -572,14 +480,13 @@ static void afs_extend_writeback(struct address_space *mapping,
static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
struct writeback_control *wbc,
struct folio *folio,
loff_t start, loff_t end)
unsigned long long start,
unsigned long long end)
{
struct afs_vnode *vnode = AFS_FS_I(mapping->host);
struct iov_iter iter;
unsigned long priv;
unsigned int offset, to, len, max_len;
loff_t i_size = i_size_read(&vnode->netfs.inode);
bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
unsigned long long i_size = i_size_read(&vnode->netfs.inode);
size_t len, max_len;
bool caching = fscache_cookie_enabled(afs_vnode_cache(vnode));
long count = wbc->nr_to_write;
int ret;
@ -597,13 +504,9 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
* immediately lockable, is not dirty or is missing, or we reach the
* end of the range.
*/
priv = (unsigned long)folio_get_private(folio);
offset = afs_folio_dirty_from(folio, priv);
to = afs_folio_dirty_to(folio, priv);
trace_afs_folio_dirty(vnode, tracepoint_string("store"), folio);
len = to - offset;
start += offset;
len = folio_size(folio);
if (start < i_size) {
/* Trim the write to the EOF; the extra data is ignored. Also
* put an upper limit on the size of a single storedata op.
@ -612,12 +515,10 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
max_len = min_t(unsigned long long, max_len, end - start + 1);
max_len = min_t(unsigned long long, max_len, i_size - start);
if (len < max_len &&
(to == folio_size(folio) || new_content))
if (len < max_len)
afs_extend_writeback(mapping, vnode, &count,
start, max_len, new_content,
caching, &len);
len = min_t(loff_t, len, max_len);
start, max_len, caching, &len);
len = min_t(unsigned long long, len, i_size - start);
}
/* We now have a contiguous set of dirty pages, each with writeback
@ -627,7 +528,7 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
folio_unlock(folio);
if (start < i_size) {
_debug("write back %x @%llx [%llx]", len, start, i_size);
_debug("write back %zx @%llx [%llx]", len, start, i_size);
/* Speculatively write to the cache. We have to fix this up
* later if the store fails.
@ -637,7 +538,7 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
ret = afs_store_data(vnode, &iter, start, false);
} else {
_debug("write discard %x @%llx [%llx]", len, start, i_size);
_debug("write discard %zx @%llx [%llx]", len, start, i_size);
/* The dirty region was entirely beyond the EOF. */
fscache_clear_page_bits(mapping, start, len, caching);
@ -693,7 +594,8 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
*/
static int afs_writepages_region(struct address_space *mapping,
struct writeback_control *wbc,
loff_t start, loff_t end, loff_t *_next,
unsigned long long start,
unsigned long long end, loff_t *_next,
bool max_one_loop)
{
struct folio *folio;
@ -905,7 +807,6 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
struct inode *inode = file_inode(file);
struct afs_vnode *vnode = AFS_FS_I(inode);
struct afs_file *af = file->private_data;
unsigned long priv;
vm_fault_t ret = VM_FAULT_RETRY;
_enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, folio_index(folio));
@ -929,24 +830,15 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
if (folio_lock_killable(folio) < 0)
goto out;
/* We mustn't change folio->private until writeback is complete as that
* details the portion of the page we need to write back and we might
* need to redirty the page if there's a problem.
*/
if (folio_wait_writeback_killable(folio) < 0) {
folio_unlock(folio);
goto out;
}
priv = afs_folio_dirty(folio, 0, folio_size(folio));
priv = afs_folio_dirty_mmapped(priv);
if (folio_test_private(folio)) {
folio_change_private(folio, (void *)priv);
if (folio_test_dirty(folio))
trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite+"), folio);
} else {
folio_attach_private(folio, (void *)priv);
else
trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite"), folio);
}
file_update_time(file);
ret = VM_FAULT_LOCKED;
@ -991,30 +883,26 @@ int afs_launder_folio(struct folio *folio)
struct afs_vnode *vnode = AFS_FS_I(folio_inode(folio));
struct iov_iter iter;
struct bio_vec bv;
unsigned long priv;
unsigned int f, t;
unsigned long long fend, i_size = vnode->netfs.inode.i_size;
size_t len;
int ret = 0;
_enter("{%lx}", folio->index);
priv = (unsigned long)folio_get_private(folio);
if (folio_clear_dirty_for_io(folio)) {
f = 0;
t = folio_size(folio);
if (folio_test_private(folio)) {
f = afs_folio_dirty_from(folio, priv);
t = afs_folio_dirty_to(folio, priv);
}
if (folio_clear_dirty_for_io(folio) && folio_pos(folio) < i_size) {
len = folio_size(folio);
fend = folio_pos(folio) + len;
if (vnode->netfs.inode.i_size < fend)
len = fend - i_size;
bvec_set_folio(&bv, folio, t - f, f);
iov_iter_bvec(&iter, ITER_SOURCE, &bv, 1, bv.bv_len);
bvec_set_folio(&bv, folio, len, 0);
iov_iter_bvec(&iter, WRITE, &bv, 1, len);
trace_afs_folio_dirty(vnode, tracepoint_string("launder"), folio);
ret = afs_store_data(vnode, &iter, folio_pos(folio) + f, true);
ret = afs_store_data(vnode, &iter, folio_pos(folio), true);
}
trace_afs_folio_dirty(vnode, tracepoint_string("laundered"), folio);
folio_detach_private(folio);
folio_wait_fscache(folio);
return ret;
}

16
include/trace/events/afs.h
View File

@ -846,26 +846,18 @@ TRACE_EVENT(afs_folio_dirty,
__field(struct afs_vnode *, vnode)
__field(const char *, where)
__field(pgoff_t, index)
__field(unsigned long, from)
__field(unsigned long, to)
__field(size_t, size)
),
TP_fast_assign(
unsigned long priv = (unsigned long)folio_get_private(folio);
__entry->vnode = vnode;
__entry->where = where;
__entry->index = folio_index(folio);
__entry->from = afs_folio_dirty_from(folio, priv);
__entry->to = afs_folio_dirty_to(folio, priv);
__entry->to |= (afs_is_folio_dirty_mmapped(priv) ?
(1UL << (BITS_PER_LONG - 1)) : 0);
__entry->size = folio_size(folio);
),
TP_printk("vn=%p %lx %s %lx-%lx%s",
__entry->vnode, __entry->index, __entry->where,
__entry->from,
__entry->to & ~(1UL << (BITS_PER_LONG - 1)),
__entry->to & (1UL << (BITS_PER_LONG - 1)) ? " M" : "")
TP_printk("vn=%p ix=%05lx s=%05lx %s",
__entry->vnode, __entry->index, __entry->size, __entry->where)
);
TRACE_EVENT(afs_call_state,