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btrfs: move fiemap code into its own file

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Currently the core of the fiemap code lives in extent_io.c, which does
not make any sense because it's not related to extent IO at all (and it
was not as well before the big rewrite of fiemap I did some time ago).
The entry point for fiemap, btrfs_fiemap(), lives in inode.c since it's
an inode operation.

Since there's a significant amount of fiemap code, move all of it into a
dedicated file, including its entry point inode.c:btrfs_fiemap().

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2024-05-22 15:29:05 +01:00 committed by David Sterba
parent f9763e4d15
commit 8996f61ab9
6 changed files with 943 additions and 925 deletions
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2
fs/btrfs/Makefile
View File

@ -33,7 +33,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
block-rsv.o delalloc-space.o block-group.o discard.o reflink.o \
subpage.o tree-mod-log.o extent-io-tree.o fs.o messages.o bio.o \
lru_cache.o raid-stripe-tree.o
lru_cache.o raid-stripe-tree.o fiemap.o
btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) += ref-verify.o

871
fs/btrfs/extent_io.c
View File

@ -2470,877 +2470,6 @@ bool try_release_extent_mapping(struct page *page, gfp_t mask)
return try_release_extent_state(io_tree, page, mask);
}
struct btrfs_fiemap_entry {
u64 offset;
u64 phys;
u64 len;
u32 flags;
};
/*
* Indicate the caller of emit_fiemap_extent() that it needs to unlock the file
* range from the inode's io tree, unlock the subvolume tree search path, flush
* the fiemap cache and relock the file range and research the subvolume tree.
* The value here is something negative that can't be confused with a valid
* errno value and different from 1 because that's also a return value from
* fiemap_fill_next_extent() and also it's often used to mean some btree search
* did not find a key, so make it some distinct negative value.
*/
#define BTRFS_FIEMAP_FLUSH_CACHE (-(MAX_ERRNO + 1))
/*
* Used to:
*
* - Cache the next entry to be emitted to the fiemap buffer, so that we can
* merge extents that are contiguous and can be grouped as a single one;
*
* - Store extents ready to be written to the fiemap buffer in an intermediary
* buffer. This intermediary buffer is to ensure that in case the fiemap
* buffer is memory mapped to the fiemap target file, we don't deadlock
* during btrfs_page_mkwrite(). This is because during fiemap we are locking
* an extent range in order to prevent races with delalloc flushing and
* ordered extent completion, which is needed in order to reliably detect
* delalloc in holes and prealloc extents. And this can lead to a deadlock
* if the fiemap buffer is memory mapped to the file we are running fiemap
* against (a silly, useless in practice scenario, but possible) because
* btrfs_page_mkwrite() will try to lock the same extent range.
*/
struct fiemap_cache {
/* An array of ready fiemap entries. */
struct btrfs_fiemap_entry *entries;
/* Number of entries in the entries array. */
int entries_size;
/* Index of the next entry in the entries array to write to. */
int entries_pos;
/*
* Once the entries array is full, this indicates what's the offset for
* the next file extent item we must search for in the inode's subvolume
* tree after unlocking the extent range in the inode's io tree and
* releasing the search path.
*/
u64 next_search_offset;
/*
* This matches struct fiemap_extent_info::fi_mapped_extents, we use it
* to count ourselves emitted extents and stop instead of relying on
* fiemap_fill_next_extent() because we buffer ready fiemap entries at
* the @entries array, and we want to stop as soon as we hit the max
* amount of extents to map, not just to save time but also to make the
* logic at extent_fiemap() simpler.
*/
unsigned int extents_mapped;
/* Fields for the cached extent (unsubmitted, not ready, extent). */
u64 offset;
u64 phys;
u64 len;
u32 flags;
bool cached;
};
static int flush_fiemap_cache(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache)
{
for (int i = 0; i < cache->entries_pos; i++) {
struct btrfs_fiemap_entry *entry = &cache->entries[i];
int ret;
ret = fiemap_fill_next_extent(fieinfo, entry->offset,
entry->phys, entry->len,
entry->flags);
/*
* Ignore 1 (reached max entries) because we keep track of that
* ourselves in emit_fiemap_extent().
*/
if (ret < 0)
return ret;
}
cache->entries_pos = 0;
return 0;
}
/*
* Helper to submit fiemap extent.
*
* Will try to merge current fiemap extent specified by @offset, @phys,
* @len and @flags with cached one.
* And only when we fails to merge, cached one will be submitted as
* fiemap extent.
*
* Return value is the same as fiemap_fill_next_extent().
*/
static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
u64 offset, u64 phys, u64 len, u32 flags)
{
struct btrfs_fiemap_entry *entry;
u64 cache_end;
/* Set at the end of extent_fiemap(). */
ASSERT((flags & FIEMAP_EXTENT_LAST) == 0);
if (!cache->cached)
goto assign;
/*
* When iterating the extents of the inode, at extent_fiemap(), we may
* find an extent that starts at an offset behind the end offset of the
* previous extent we processed. This happens if fiemap is called
* without FIEMAP_FLAG_SYNC and there are ordered extents completing
* after we had to unlock the file range, release the search path, emit
* the fiemap extents stored in the buffer (cache->entries array) and
* the lock the remainder of the range and re-search the btree.
*
* For example we are in leaf X processing its last item, which is the
* file extent item for file range [512K, 1M[, and after
* btrfs_next_leaf() releases the path, there's an ordered extent that
* completes for the file range [768K, 2M[, and that results in trimming
* the file extent item so that it now corresponds to the file range
* [512K, 768K[ and a new file extent item is inserted for the file
* range [768K, 2M[, which may end up as the last item of leaf X or as
* the first item of the next leaf - in either case btrfs_next_leaf()
* will leave us with a path pointing to the new extent item, for the
* file range [768K, 2M[, since that's the first key that follows the
* last one we processed. So in order not to report overlapping extents
* to user space, we trim the length of the previously cached extent and
* emit it.
*
* Upon calling btrfs_next_leaf() we may also find an extent with an
* offset smaller than or equals to cache->offset, and this happens
* when we had a hole or prealloc extent with several delalloc ranges in
* it, but after btrfs_next_leaf() released the path, delalloc was
* flushed and the resulting ordered extents were completed, so we can
* now have found a file extent item for an offset that is smaller than
* or equals to what we have in cache->offset. We deal with this as
* described below.
*/
cache_end = cache->offset + cache->len;
if (cache_end > offset) {
if (offset == cache->offset) {
/*
* We cached a dealloc range (found in the io tree) for
* a hole or prealloc extent and we have now found a
* file extent item for the same offset. What we have
* now is more recent and up to date, so discard what
* we had in the cache and use what we have just found.
*/
goto assign;
} else if (offset > cache->offset) {
/*
* The extent range we previously found ends after the
* offset of the file extent item we found and that
* offset falls somewhere in the middle of that previous
* extent range. So adjust the range we previously found
* to end at the offset of the file extent item we have
* just found, since this extent is more up to date.
* Emit that adjusted range and cache the file extent
* item we have just found. This corresponds to the case
* where a previously found file extent item was split
* due to an ordered extent completing.
*/
cache->len = offset - cache->offset;
goto emit;
} else {
const u64 range_end = offset + len;
/*
* The offset of the file extent item we have just found
* is behind the cached offset. This means we were
* processing a hole or prealloc extent for which we
* have found delalloc ranges (in the io tree), so what
* we have in the cache is the last delalloc range we
* found while the file extent item we found can be
* either for a whole delalloc range we previously
* emmitted or only a part of that range.
*
* We have two cases here:
*
* 1) The file extent item's range ends at or behind the
* cached extent's end. In this case just ignore the
* current file extent item because we don't want to
* overlap with previous ranges that may have been
* emmitted already;
*
* 2) The file extent item starts behind the currently
* cached extent but its end offset goes beyond the
* end offset of the cached extent. We don't want to
* overlap with a previous range that may have been
* emmitted already, so we emit the currently cached
* extent and then partially store the current file
* extent item's range in the cache, for the subrange
* going the cached extent's end to the end of the
* file extent item.
*/
if (range_end <= cache_end)
return 0;
if (!(flags & (FIEMAP_EXTENT_ENCODED | FIEMAP_EXTENT_DELALLOC)))
phys += cache_end - offset;
offset = cache_end;
len = range_end - cache_end;
goto emit;
}
}
/*
* Only merges fiemap extents if
* 1) Their logical addresses are continuous
*
* 2) Their physical addresses are continuous
* So truly compressed (physical size smaller than logical size)
* extents won't get merged with each other
*
* 3) Share same flags
*/
if (cache->offset + cache->len == offset &&
cache->phys + cache->len == phys &&
cache->flags == flags) {
cache->len += len;
return 0;
}
emit:
/* Not mergeable, need to submit cached one */
if (cache->entries_pos == cache->entries_size) {
/*
* We will need to research for the end offset of the last
* stored extent and not from the current offset, because after
* unlocking the range and releasing the path, if there's a hole
* between that end offset and this current offset, a new extent
* may have been inserted due to a new write, so we don't want
* to miss it.
*/
entry = &cache->entries[cache->entries_size - 1];
cache->next_search_offset = entry->offset + entry->len;
cache->cached = false;
return BTRFS_FIEMAP_FLUSH_CACHE;
}
entry = &cache->entries[cache->entries_pos];
entry->offset = cache->offset;
entry->phys = cache->phys;
entry->len = cache->len;
entry->flags = cache->flags;
cache->entries_pos++;
cache->extents_mapped++;
if (cache->extents_mapped == fieinfo->fi_extents_max) {
cache->cached = false;
return 1;
}
assign:
cache->cached = true;
cache->offset = offset;
cache->phys = phys;
cache->len = len;
cache->flags = flags;
return 0;
}
/*
* Emit last fiemap cache
*
* The last fiemap cache may still be cached in the following case:
* 0 4k 8k
* |<- Fiemap range ->|
* |<------------ First extent ----------->|
*
* In this case, the first extent range will be cached but not emitted.
* So we must emit it before ending extent_fiemap().
*/
static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache)
{
int ret;
if (!cache->cached)
return 0;
ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
cache->len, cache->flags);
cache->cached = false;
if (ret > 0)
ret = 0;
return ret;
}
static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path)
{
struct extent_buffer *clone = path->nodes[0];
struct btrfs_key key;
int slot;
int ret;
path->slots[0]++;
if (path->slots[0] < btrfs_header_nritems(path->nodes[0]))
return 0;
/*
* Add a temporary extra ref to an already cloned extent buffer to
* prevent btrfs_next_leaf() freeing it, we want to reuse it to avoid
* the cost of allocating a new one.
*/
ASSERT(test_bit(EXTENT_BUFFER_UNMAPPED, &clone->bflags));
atomic_inc(&clone->refs);
ret = btrfs_next_leaf(inode->root, path);
if (ret != 0)
goto out;
/*
* Don't bother with cloning if there are no more file extent items for
* our inode.
*/
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) {
ret = 1;
goto out;
}
/*
* Important to preserve the start field, for the optimizations when
* checking if extents are shared (see extent_fiemap()).
*
* We must set ->start before calling copy_extent_buffer_full(). If we
* are on sub-pagesize blocksize, we use ->start to determine the offset
* into the folio where our eb exists, and if we update ->start after
* the fact then any subsequent reads of the eb may read from a
* different offset in the folio than where we originally copied into.
*/
clone->start = path->nodes[0]->start;
/* See the comment at fiemap_search_slot() about why we clone. */
copy_extent_buffer_full(clone, path->nodes[0]);
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
out:
if (ret)
free_extent_buffer(clone);
return ret;
}
/*
* Search for the first file extent item that starts at a given file offset or
* the one that starts immediately before that offset.
* Returns: 0 on success, < 0 on error, 1 if not found.
*/
static int fiemap_search_slot(struct btrfs_inode *inode, struct btrfs_path *path,
u64 file_offset)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *clone;
struct btrfs_key key;
int slot;
int ret;
key.objectid = ino;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = file_offset;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
return ret;
if (ret > 0 && path->slots[0] > 0) {
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0] - 1);
if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY)
path->slots[0]--;
}
if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
ret = btrfs_next_leaf(root, path);
if (ret != 0)
return ret;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
return 1;
}
/*
* We clone the leaf and use it during fiemap. This is because while
* using the leaf we do expensive things like checking if an extent is
* shared, which can take a long time. In order to prevent blocking
* other tasks for too long, we use a clone of the leaf. We have locked
* the file range in the inode's io tree, so we know none of our file
* extent items can change. This way we avoid blocking other tasks that
* want to insert items for other inodes in the same leaf or b+tree
* rebalance operations (triggered for example when someone is trying
* to push items into this leaf when trying to insert an item in a
* neighbour leaf).
* We also need the private clone because holding a read lock on an
* extent buffer of the subvolume's b+tree will make lockdep unhappy
* when we check if extents are shared, as backref walking may need to
* lock the same leaf we are processing.
*/
clone = btrfs_clone_extent_buffer(path->nodes[0]);
if (!clone)
return -ENOMEM;
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
return 0;
}
/*
* Process a range which is a hole or a prealloc extent in the inode's subvolume
* btree. If @disk_bytenr is 0, we are dealing with a hole, otherwise a prealloc
* extent. The end offset (@end) is inclusive.
*/
static int fiemap_process_hole(struct btrfs_inode *inode,
struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
struct extent_state **delalloc_cached_state,
struct btrfs_backref_share_check_ctx *backref_ctx,
u64 disk_bytenr, u64 extent_offset,
u64 extent_gen,
u64 start, u64 end)
{
const u64 i_size = i_size_read(&inode->vfs_inode);
u64 cur_offset = start;
u64 last_delalloc_end = 0;
u32 prealloc_flags = FIEMAP_EXTENT_UNWRITTEN;
bool checked_extent_shared = false;
int ret;
/*
* There can be no delalloc past i_size, so don't waste time looking for
* it beyond i_size.
*/
while (cur_offset < end && cur_offset < i_size) {
u64 delalloc_start;
u64 delalloc_end;
u64 prealloc_start;
u64 prealloc_len = 0;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode, cur_offset, end,
delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
break;
/*
* If this is a prealloc extent we have to report every section
* of it that has no delalloc.
*/
if (disk_bytenr != 0) {
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = delalloc_start - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = delalloc_start - prealloc_start;
}
}
if (prealloc_len > 0) {
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
checked_extent_shared = true;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
extent_offset += prealloc_len;
}
ret = emit_fiemap_extent(fieinfo, cache, delalloc_start, 0,
delalloc_end + 1 - delalloc_start,
FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
if (ret)
return ret;
last_delalloc_end = delalloc_end;
cur_offset = delalloc_end + 1;
extent_offset += cur_offset - delalloc_start;
cond_resched();
}
/*
* Either we found no delalloc for the whole prealloc extent or we have
* a prealloc extent that spans i_size or starts at or after i_size.
*/
if (disk_bytenr != 0 && last_delalloc_end < end) {
u64 prealloc_start;
u64 prealloc_len;
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = end + 1 - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = end + 1 - prealloc_start;
}
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
}
return 0;
}
static int fiemap_find_last_extent_offset(struct btrfs_inode *inode,
struct btrfs_path *path,
u64 *last_extent_end_ret)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *leaf;
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 disk_bytenr;
int ret;
/*
* Lookup the last file extent. We're not using i_size here because
* there might be preallocation past i_size.
*/
ret = btrfs_lookup_file_extent(NULL, root, path, ino, (u64)-1, 0);
/* There can't be a file extent item at offset (u64)-1 */
ASSERT(ret != 0);
if (ret < 0)
return ret;
/*
* For a non-existing key, btrfs_search_slot() always leaves us at a
* slot > 0, except if the btree is empty, which is impossible because
* at least it has the inode item for this inode and all the items for
* the root inode 256.
*/
ASSERT(path->slots[0] > 0);
path->slots[0]--;
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) {
/* No file extent items in the subvolume tree. */
*last_extent_end_ret = 0;
return 0;
}
/*
* For an inline extent, the disk_bytenr is where inline data starts at,
* so first check if we have an inline extent item before checking if we
* have an implicit hole (disk_bytenr == 0).
*/
ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item);
if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_INLINE) {
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
/*
* Find the last file extent item that is not a hole (when NO_HOLES is
* not enabled). This should take at most 2 iterations in the worst
* case: we have one hole file extent item at slot 0 of a leaf and
* another hole file extent item as the last item in the previous leaf.
* This is because we merge file extent items that represent holes.
*/
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
while (disk_bytenr == 0) {
ret = btrfs_previous_item(root, path, ino, BTRFS_EXTENT_DATA_KEY);
if (ret < 0) {
return ret;
} else if (ret > 0) {
/* No file extent items that are not holes. */
*last_extent_end_ret = 0;
return 0;
}
leaf = path->nodes[0];
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
}
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
const u64 ino = btrfs_ino(inode);
struct extent_state *cached_state = NULL;
struct extent_state *delalloc_cached_state = NULL;
struct btrfs_path *path;
struct fiemap_cache cache = { 0 };
struct btrfs_backref_share_check_ctx *backref_ctx;
u64 last_extent_end;
u64 prev_extent_end;
u64 range_start;
u64 range_end;
const u64 sectorsize = inode->root->fs_info->sectorsize;
bool stopped = false;
int ret;
cache.entries_size = PAGE_SIZE / sizeof(struct btrfs_fiemap_entry);
cache.entries = kmalloc_array(cache.entries_size,
sizeof(struct btrfs_fiemap_entry),
GFP_KERNEL);
backref_ctx = btrfs_alloc_backref_share_check_ctx();
path = btrfs_alloc_path();
if (!cache.entries || !backref_ctx || !path) {
ret = -ENOMEM;
goto out;
}
restart:
range_start = round_down(start, sectorsize);
range_end = round_up(start + len, sectorsize);
prev_extent_end = range_start;
lock_extent(&inode->io_tree, range_start, range_end, &cached_state);
ret = fiemap_find_last_extent_offset(inode, path, &last_extent_end);
if (ret < 0)
goto out_unlock;
btrfs_release_path(path);
path->reada = READA_FORWARD;
ret = fiemap_search_slot(inode, path, range_start);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/*
* No file extent item found, but we may have delalloc between
* the current offset and i_size. So check for that.
*/
ret = 0;
goto check_eof_delalloc;
}
while (prev_extent_end < range_end) {
struct extent_buffer *leaf = path->nodes[0];
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 extent_end;
u64 extent_len;
u64 extent_offset = 0;
u64 extent_gen;
u64 disk_bytenr = 0;
u64 flags = 0;
int extent_type;
u8 compression;
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
break;
extent_end = btrfs_file_extent_end(path);
/*
* The first iteration can leave us at an extent item that ends
* before our range's start. Move to the next item.
*/
if (extent_end <= range_start)
goto next_item;
backref_ctx->curr_leaf_bytenr = leaf->start;
/* We have in implicit hole (NO_HOLES feature enabled). */
if (prev_extent_end < key.offset) {
const u64 hole_end = min(key.offset, range_end) - 1;
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
prev_extent_end, hole_end);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* fiemap_fill_next_extent() told us to stop. */
stopped = true;
break;
}
/* We've reached the end of the fiemap range, stop. */
if (key.offset >= range_end) {
stopped = true;
break;
}
}
extent_len = extent_end - key.offset;
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
compression = btrfs_file_extent_compression(leaf, ei);
extent_type = btrfs_file_extent_type(leaf, ei);
extent_gen = btrfs_file_extent_generation(leaf, ei);
if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
if (compression == BTRFS_COMPRESS_NONE)
extent_offset = btrfs_file_extent_offset(leaf, ei);
}
if (compression != BTRFS_COMPRESS_NONE)
flags |= FIEMAP_EXTENT_ENCODED;
if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
flags |= FIEMAP_EXTENT_DATA_INLINE;
flags |= FIEMAP_EXTENT_NOT_ALIGNED;
ret = emit_fiemap_extent(fieinfo, &cache, key.offset, 0,
extent_len, flags);
} else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx,
disk_bytenr, extent_offset,
extent_gen, key.offset,
extent_end - 1);
} else if (disk_bytenr == 0) {
/* We have an explicit hole. */
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
key.offset, extent_end - 1);
} else {
/* We have a regular extent. */
if (fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
goto out_unlock;
else if (ret > 0)
flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, &cache, key.offset,
disk_bytenr + extent_offset,
extent_len, flags);
}
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* emit_fiemap_extent() told us to stop. */
stopped = true;
break;
}
prev_extent_end = extent_end;
next_item:
if (fatal_signal_pending(current)) {
ret = -EINTR;
goto out_unlock;
}
ret = fiemap_next_leaf_item(inode, path);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* No more file extent items for this inode. */
break;
}
cond_resched();
}
check_eof_delalloc:
if (!stopped && prev_extent_end < range_end) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state, backref_ctx,
0, 0, 0, prev_extent_end, range_end - 1);
if (ret < 0)
goto out_unlock;
prev_extent_end = range_end;
}
if (cache.cached && cache.offset + cache.len >= last_extent_end) {
const u64 i_size = i_size_read(&inode->vfs_inode);
if (prev_extent_end < i_size) {
u64 delalloc_start;
u64 delalloc_end;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode,
prev_extent_end,
i_size - 1,
&delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
cache.flags |= FIEMAP_EXTENT_LAST;
} else {
cache.flags |= FIEMAP_EXTENT_LAST;
}
}
out_unlock:
unlock_extent(&inode->io_tree, range_start, range_end, &cached_state);
if (ret == BTRFS_FIEMAP_FLUSH_CACHE) {
btrfs_release_path(path);
ret = flush_fiemap_cache(fieinfo, &cache);
if (ret)
goto out;
len -= cache.next_search_offset - start;
start = cache.next_search_offset;
goto restart;
} else if (ret < 0) {
goto out;
}
/*
* Must free the path before emitting to the fiemap buffer because we
* may have a non-cloned leaf and if the fiemap buffer is memory mapped
* to a file, a write into it (through btrfs_page_mkwrite()) may trigger
* waiting for an ordered extent that in order to complete needs to
* modify that leaf, therefore leading to a deadlock.
*/
btrfs_free_path(path);
path = NULL;
ret = flush_fiemap_cache(fieinfo, &cache);
if (ret)
goto out;
ret = emit_last_fiemap_cache(fieinfo, &cache);
out:
free_extent_state(delalloc_cached_state);
kfree(cache.entries);
btrfs_free_backref_share_ctx(backref_ctx);
btrfs_free_path(path);
return ret;
}
static void __free_extent_buffer(struct extent_buffer *eb)
{
kmem_cache_free(extent_buffer_cache, eb);

2
fs/btrfs/extent_io.h
View File

@ -242,8 +242,6 @@ int btrfs_writepages(struct address_space *mapping, struct writeback_control *wb
int btree_write_cache_pages(struct address_space *mapping,
struct writeback_control *wbc);
void btrfs_readahead(struct readahead_control *rac);
int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len);
int set_folio_extent_mapped(struct folio *folio);
int set_page_extent_mapped(struct page *page);
void clear_page_extent_mapped(struct page *page);

930
fs/btrfs/fiemap.c Normal file
View File

@ -0,0 +1,930 @@
// SPDX-License-Identifier: GPL-2.0
#include "backref.h"
#include "btrfs_inode.h"
#include "fiemap.h"
#include "file.h"
#include "file-item.h"
struct btrfs_fiemap_entry {
u64 offset;
u64 phys;
u64 len;
u32 flags;
};
/*
* Indicate the caller of emit_fiemap_extent() that it needs to unlock the file
* range from the inode's io tree, unlock the subvolume tree search path, flush
* the fiemap cache and relock the file range and research the subvolume tree.
* The value here is something negative that can't be confused with a valid
* errno value and different from 1 because that's also a return value from
* fiemap_fill_next_extent() and also it's often used to mean some btree search
* did not find a key, so make it some distinct negative value.
*/
#define BTRFS_FIEMAP_FLUSH_CACHE (-(MAX_ERRNO + 1))
/*
* Used to:
*
* - Cache the next entry to be emitted to the fiemap buffer, so that we can
* merge extents that are contiguous and can be grouped as a single one;
*
* - Store extents ready to be written to the fiemap buffer in an intermediary
* buffer. This intermediary buffer is to ensure that in case the fiemap
* buffer is memory mapped to the fiemap target file, we don't deadlock
* during btrfs_page_mkwrite(). This is because during fiemap we are locking
* an extent range in order to prevent races with delalloc flushing and
* ordered extent completion, which is needed in order to reliably detect
* delalloc in holes and prealloc extents. And this can lead to a deadlock
* if the fiemap buffer is memory mapped to the file we are running fiemap
* against (a silly, useless in practice scenario, but possible) because
* btrfs_page_mkwrite() will try to lock the same extent range.
*/
struct fiemap_cache {
/* An array of ready fiemap entries. */
struct btrfs_fiemap_entry *entries;
/* Number of entries in the entries array. */
int entries_size;
/* Index of the next entry in the entries array to write to. */
int entries_pos;
/*
* Once the entries array is full, this indicates what's the offset for
* the next file extent item we must search for in the inode's subvolume
* tree after unlocking the extent range in the inode's io tree and
* releasing the search path.
*/
u64 next_search_offset;
/*
* This matches struct fiemap_extent_info::fi_mapped_extents, we use it
* to count ourselves emitted extents and stop instead of relying on
* fiemap_fill_next_extent() because we buffer ready fiemap entries at
* the @entries array, and we want to stop as soon as we hit the max
* amount of extents to map, not just to save time but also to make the
* logic at extent_fiemap() simpler.
*/
unsigned int extents_mapped;
/* Fields for the cached extent (unsubmitted, not ready, extent). */
u64 offset;
u64 phys;
u64 len;
u32 flags;
bool cached;
};
static int flush_fiemap_cache(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache)
{
for (int i = 0; i < cache->entries_pos; i++) {
struct btrfs_fiemap_entry *entry = &cache->entries[i];
int ret;
ret = fiemap_fill_next_extent(fieinfo, entry->offset,
entry->phys, entry->len,
entry->flags);
/*
* Ignore 1 (reached max entries) because we keep track of that
* ourselves in emit_fiemap_extent().
*/
if (ret < 0)
return ret;
}
cache->entries_pos = 0;
return 0;
}
/*
* Helper to submit fiemap extent.
*
* Will try to merge current fiemap extent specified by @offset, @phys,
* @len and @flags with cached one.
* And only when we fails to merge, cached one will be submitted as
* fiemap extent.
*
* Return value is the same as fiemap_fill_next_extent().
*/
static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
u64 offset, u64 phys, u64 len, u32 flags)
{
struct btrfs_fiemap_entry *entry;
u64 cache_end;
/* Set at the end of extent_fiemap(). */
ASSERT((flags & FIEMAP_EXTENT_LAST) == 0);
if (!cache->cached)
goto assign;
/*
* When iterating the extents of the inode, at extent_fiemap(), we may
* find an extent that starts at an offset behind the end offset of the
* previous extent we processed. This happens if fiemap is called
* without FIEMAP_FLAG_SYNC and there are ordered extents completing
* after we had to unlock the file range, release the search path, emit
* the fiemap extents stored in the buffer (cache->entries array) and
* the lock the remainder of the range and re-search the btree.
*
* For example we are in leaf X processing its last item, which is the
* file extent item for file range [512K, 1M[, and after
* btrfs_next_leaf() releases the path, there's an ordered extent that
* completes for the file range [768K, 2M[, and that results in trimming
* the file extent item so that it now corresponds to the file range
* [512K, 768K[ and a new file extent item is inserted for the file
* range [768K, 2M[, which may end up as the last item of leaf X or as
* the first item of the next leaf - in either case btrfs_next_leaf()
* will leave us with a path pointing to the new extent item, for the
* file range [768K, 2M[, since that's the first key that follows the
* last one we processed. So in order not to report overlapping extents
* to user space, we trim the length of the previously cached extent and
* emit it.
*
* Upon calling btrfs_next_leaf() we may also find an extent with an
* offset smaller than or equals to cache->offset, and this happens
* when we had a hole or prealloc extent with several delalloc ranges in
* it, but after btrfs_next_leaf() released the path, delalloc was
* flushed and the resulting ordered extents were completed, so we can
* now have found a file extent item for an offset that is smaller than
* or equals to what we have in cache->offset. We deal with this as
* described below.
*/
cache_end = cache->offset + cache->len;
if (cache_end > offset) {
if (offset == cache->offset) {
/*
* We cached a dealloc range (found in the io tree) for
* a hole or prealloc extent and we have now found a
* file extent item for the same offset. What we have
* now is more recent and up to date, so discard what
* we had in the cache and use what we have just found.
*/
goto assign;
} else if (offset > cache->offset) {
/*
* The extent range we previously found ends after the
* offset of the file extent item we found and that
* offset falls somewhere in the middle of that previous
* extent range. So adjust the range we previously found
* to end at the offset of the file extent item we have
* just found, since this extent is more up to date.
* Emit that adjusted range and cache the file extent
* item we have just found. This corresponds to the case
* where a previously found file extent item was split
* due to an ordered extent completing.
*/
cache->len = offset - cache->offset;
goto emit;
} else {
const u64 range_end = offset + len;
/*
* The offset of the file extent item we have just found
* is behind the cached offset. This means we were
* processing a hole or prealloc extent for which we
* have found delalloc ranges (in the io tree), so what
* we have in the cache is the last delalloc range we
* found while the file extent item we found can be
* either for a whole delalloc range we previously
* emmitted or only a part of that range.
*
* We have two cases here:
*
* 1) The file extent item's range ends at or behind the
* cached extent's end. In this case just ignore the
* current file extent item because we don't want to
* overlap with previous ranges that may have been
* emmitted already;
*
* 2) The file extent item starts behind the currently
* cached extent but its end offset goes beyond the
* end offset of the cached extent. We don't want to
* overlap with a previous range that may have been
* emmitted already, so we emit the currently cached
* extent and then partially store the current file
* extent item's range in the cache, for the subrange
* going the cached extent's end to the end of the
* file extent item.
*/
if (range_end <= cache_end)
return 0;
if (!(flags & (FIEMAP_EXTENT_ENCODED | FIEMAP_EXTENT_DELALLOC)))
phys += cache_end - offset;
offset = cache_end;
len = range_end - cache_end;
goto emit;
}
}
/*
* Only merges fiemap extents if
* 1) Their logical addresses are continuous
*
* 2) Their physical addresses are continuous
* So truly compressed (physical size smaller than logical size)
* extents won't get merged with each other
*
* 3) Share same flags
*/
if (cache->offset + cache->len == offset &&
cache->phys + cache->len == phys &&
cache->flags == flags) {
cache->len += len;
return 0;
}
emit:
/* Not mergeable, need to submit cached one */
if (cache->entries_pos == cache->entries_size) {
/*
* We will need to research for the end offset of the last
* stored extent and not from the current offset, because after
* unlocking the range and releasing the path, if there's a hole
* between that end offset and this current offset, a new extent
* may have been inserted due to a new write, so we don't want
* to miss it.
*/
entry = &cache->entries[cache->entries_size - 1];
cache->next_search_offset = entry->offset + entry->len;
cache->cached = false;
return BTRFS_FIEMAP_FLUSH_CACHE;
}
entry = &cache->entries[cache->entries_pos];
entry->offset = cache->offset;
entry->phys = cache->phys;
entry->len = cache->len;
entry->flags = cache->flags;
cache->entries_pos++;
cache->extents_mapped++;
if (cache->extents_mapped == fieinfo->fi_extents_max) {
cache->cached = false;
return 1;
}
assign:
cache->cached = true;
cache->offset = offset;
cache->phys = phys;
cache->len = len;
cache->flags = flags;
return 0;
}
/*
* Emit last fiemap cache
*
* The last fiemap cache may still be cached in the following case:
* 0 4k 8k
* |<- Fiemap range ->|
* |<------------ First extent ----------->|
*
* In this case, the first extent range will be cached but not emitted.
* So we must emit it before ending extent_fiemap().
*/
static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache)
{
int ret;
if (!cache->cached)
return 0;
ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
cache->len, cache->flags);
cache->cached = false;
if (ret > 0)
ret = 0;
return ret;
}
static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path)
{
struct extent_buffer *clone = path->nodes[0];
struct btrfs_key key;
int slot;
int ret;
path->slots[0]++;
if (path->slots[0] < btrfs_header_nritems(path->nodes[0]))
return 0;
/*
* Add a temporary extra ref to an already cloned extent buffer to
* prevent btrfs_next_leaf() freeing it, we want to reuse it to avoid
* the cost of allocating a new one.
*/
ASSERT(test_bit(EXTENT_BUFFER_UNMAPPED, &clone->bflags));
atomic_inc(&clone->refs);
ret = btrfs_next_leaf(inode->root, path);
if (ret != 0)
goto out;
/*
* Don't bother with cloning if there are no more file extent items for
* our inode.
*/
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) {
ret = 1;
goto out;
}
/*
* Important to preserve the start field, for the optimizations when
* checking if extents are shared (see extent_fiemap()).
*
* We must set ->start before calling copy_extent_buffer_full(). If we
* are on sub-pagesize blocksize, we use ->start to determine the offset
* into the folio where our eb exists, and if we update ->start after
* the fact then any subsequent reads of the eb may read from a
* different offset in the folio than where we originally copied into.
*/
clone->start = path->nodes[0]->start;
/* See the comment at fiemap_search_slot() about why we clone. */
copy_extent_buffer_full(clone, path->nodes[0]);
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
out:
if (ret)
free_extent_buffer(clone);
return ret;
}
/*
* Search for the first file extent item that starts at a given file offset or
* the one that starts immediately before that offset.
* Returns: 0 on success, < 0 on error, 1 if not found.
*/
static int fiemap_search_slot(struct btrfs_inode *inode, struct btrfs_path *path,
u64 file_offset)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *clone;
struct btrfs_key key;
int slot;
int ret;
key.objectid = ino;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = file_offset;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
return ret;
if (ret > 0 && path->slots[0] > 0) {
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0] - 1);
if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY)
path->slots[0]--;
}
if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
ret = btrfs_next_leaf(root, path);
if (ret != 0)
return ret;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
return 1;
}
/*
* We clone the leaf and use it during fiemap. This is because while
* using the leaf we do expensive things like checking if an extent is
* shared, which can take a long time. In order to prevent blocking
* other tasks for too long, we use a clone of the leaf. We have locked
* the file range in the inode's io tree, so we know none of our file
* extent items can change. This way we avoid blocking other tasks that
* want to insert items for other inodes in the same leaf or b+tree
* rebalance operations (triggered for example when someone is trying
* to push items into this leaf when trying to insert an item in a
* neighbour leaf).
* We also need the private clone because holding a read lock on an
* extent buffer of the subvolume's b+tree will make lockdep unhappy
* when we check if extents are shared, as backref walking may need to
* lock the same leaf we are processing.
*/
clone = btrfs_clone_extent_buffer(path->nodes[0]);
if (!clone)
return -ENOMEM;
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
return 0;
}
/*
* Process a range which is a hole or a prealloc extent in the inode's subvolume
* btree. If @disk_bytenr is 0, we are dealing with a hole, otherwise a prealloc
* extent. The end offset (@end) is inclusive.
*/
static int fiemap_process_hole(struct btrfs_inode *inode,
struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
struct extent_state **delalloc_cached_state,
struct btrfs_backref_share_check_ctx *backref_ctx,
u64 disk_bytenr, u64 extent_offset,
u64 extent_gen,
u64 start, u64 end)
{
const u64 i_size = i_size_read(&inode->vfs_inode);
u64 cur_offset = start;
u64 last_delalloc_end = 0;
u32 prealloc_flags = FIEMAP_EXTENT_UNWRITTEN;
bool checked_extent_shared = false;
int ret;
/*
* There can be no delalloc past i_size, so don't waste time looking for
* it beyond i_size.
*/
while (cur_offset < end && cur_offset < i_size) {
u64 delalloc_start;
u64 delalloc_end;
u64 prealloc_start;
u64 prealloc_len = 0;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode, cur_offset, end,
delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
break;
/*
* If this is a prealloc extent we have to report every section
* of it that has no delalloc.
*/
if (disk_bytenr != 0) {
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = delalloc_start - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = delalloc_start - prealloc_start;
}
}
if (prealloc_len > 0) {
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
checked_extent_shared = true;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
extent_offset += prealloc_len;
}
ret = emit_fiemap_extent(fieinfo, cache, delalloc_start, 0,
delalloc_end + 1 - delalloc_start,
FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
if (ret)
return ret;
last_delalloc_end = delalloc_end;
cur_offset = delalloc_end + 1;
extent_offset += cur_offset - delalloc_start;
cond_resched();
}
/*
* Either we found no delalloc for the whole prealloc extent or we have
* a prealloc extent that spans i_size or starts at or after i_size.
*/
if (disk_bytenr != 0 && last_delalloc_end < end) {
u64 prealloc_start;
u64 prealloc_len;
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = end + 1 - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = end + 1 - prealloc_start;
}
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
}
return 0;
}
static int fiemap_find_last_extent_offset(struct btrfs_inode *inode,
struct btrfs_path *path,
u64 *last_extent_end_ret)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *leaf;
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 disk_bytenr;
int ret;
/*
* Lookup the last file extent. We're not using i_size here because
* there might be preallocation past i_size.
*/
ret = btrfs_lookup_file_extent(NULL, root, path, ino, (u64)-1, 0);
/* There can't be a file extent item at offset (u64)-1 */
ASSERT(ret != 0);
if (ret < 0)
return ret;
/*
* For a non-existing key, btrfs_search_slot() always leaves us at a
* slot > 0, except if the btree is empty, which is impossible because
* at least it has the inode item for this inode and all the items for
* the root inode 256.
*/
ASSERT(path->slots[0] > 0);
path->slots[0]--;
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) {
/* No file extent items in the subvolume tree. */
*last_extent_end_ret = 0;
return 0;
}
/*
* For an inline extent, the disk_bytenr is where inline data starts at,
* so first check if we have an inline extent item before checking if we
* have an implicit hole (disk_bytenr == 0).
*/
ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item);
if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_INLINE) {
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
/*
* Find the last file extent item that is not a hole (when NO_HOLES is
* not enabled). This should take at most 2 iterations in the worst
* case: we have one hole file extent item at slot 0 of a leaf and
* another hole file extent item as the last item in the previous leaf.
* This is because we merge file extent items that represent holes.
*/
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
while (disk_bytenr == 0) {
ret = btrfs_previous_item(root, path, ino, BTRFS_EXTENT_DATA_KEY);
if (ret < 0) {
return ret;
} else if (ret > 0) {
/* No file extent items that are not holes. */
*last_extent_end_ret = 0;
return 0;
}
leaf = path->nodes[0];
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
}
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
static int extent_fiemap(struct btrfs_inode *inode,
struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
const u64 ino = btrfs_ino(inode);
struct extent_state *cached_state = NULL;
struct extent_state *delalloc_cached_state = NULL;
struct btrfs_path *path;
struct fiemap_cache cache = { 0 };
struct btrfs_backref_share_check_ctx *backref_ctx;
u64 last_extent_end;
u64 prev_extent_end;
u64 range_start;
u64 range_end;
const u64 sectorsize = inode->root->fs_info->sectorsize;
bool stopped = false;
int ret;
cache.entries_size = PAGE_SIZE / sizeof(struct btrfs_fiemap_entry);
cache.entries = kmalloc_array(cache.entries_size,
sizeof(struct btrfs_fiemap_entry),
GFP_KERNEL);
backref_ctx = btrfs_alloc_backref_share_check_ctx();
path = btrfs_alloc_path();
if (!cache.entries || !backref_ctx || !path) {
ret = -ENOMEM;
goto out;
}
restart:
range_start = round_down(start, sectorsize);
range_end = round_up(start + len, sectorsize);
prev_extent_end = range_start;
lock_extent(&inode->io_tree, range_start, range_end, &cached_state);
ret = fiemap_find_last_extent_offset(inode, path, &last_extent_end);
if (ret < 0)
goto out_unlock;
btrfs_release_path(path);
path->reada = READA_FORWARD;
ret = fiemap_search_slot(inode, path, range_start);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/*
* No file extent item found, but we may have delalloc between
* the current offset and i_size. So check for that.
*/
ret = 0;
goto check_eof_delalloc;
}
while (prev_extent_end < range_end) {
struct extent_buffer *leaf = path->nodes[0];
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 extent_end;
u64 extent_len;
u64 extent_offset = 0;
u64 extent_gen;
u64 disk_bytenr = 0;
u64 flags = 0;
int extent_type;
u8 compression;
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
break;
extent_end = btrfs_file_extent_end(path);
/*
* The first iteration can leave us at an extent item that ends
* before our range's start. Move to the next item.
*/
if (extent_end <= range_start)
goto next_item;
backref_ctx->curr_leaf_bytenr = leaf->start;
/* We have in implicit hole (NO_HOLES feature enabled). */
if (prev_extent_end < key.offset) {
const u64 hole_end = min(key.offset, range_end) - 1;
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
prev_extent_end, hole_end);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* fiemap_fill_next_extent() told us to stop. */
stopped = true;
break;
}
/* We've reached the end of the fiemap range, stop. */
if (key.offset >= range_end) {
stopped = true;
break;
}
}
extent_len = extent_end - key.offset;
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
compression = btrfs_file_extent_compression(leaf, ei);
extent_type = btrfs_file_extent_type(leaf, ei);
extent_gen = btrfs_file_extent_generation(leaf, ei);
if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
if (compression == BTRFS_COMPRESS_NONE)
extent_offset = btrfs_file_extent_offset(leaf, ei);
}
if (compression != BTRFS_COMPRESS_NONE)
flags |= FIEMAP_EXTENT_ENCODED;
if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
flags |= FIEMAP_EXTENT_DATA_INLINE;
flags |= FIEMAP_EXTENT_NOT_ALIGNED;
ret = emit_fiemap_extent(fieinfo, &cache, key.offset, 0,
extent_len, flags);
} else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx,
disk_bytenr, extent_offset,
extent_gen, key.offset,
extent_end - 1);
} else if (disk_bytenr == 0) {
/* We have an explicit hole. */
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
key.offset, extent_end - 1);
} else {
/* We have a regular extent. */
if (fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
goto out_unlock;
else if (ret > 0)
flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, &cache, key.offset,
disk_bytenr + extent_offset,
extent_len, flags);
}
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* emit_fiemap_extent() told us to stop. */
stopped = true;
break;
}
prev_extent_end = extent_end;
next_item:
if (fatal_signal_pending(current)) {
ret = -EINTR;
goto out_unlock;
}
ret = fiemap_next_leaf_item(inode, path);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* No more file extent items for this inode. */
break;
}
cond_resched();
}
check_eof_delalloc:
if (!stopped && prev_extent_end < range_end) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state, backref_ctx,
0, 0, 0, prev_extent_end, range_end - 1);
if (ret < 0)
goto out_unlock;
prev_extent_end = range_end;
}
if (cache.cached && cache.offset + cache.len >= last_extent_end) {
const u64 i_size = i_size_read(&inode->vfs_inode);
if (prev_extent_end < i_size) {
u64 delalloc_start;
u64 delalloc_end;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode,
prev_extent_end,
i_size - 1,
&delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
cache.flags |= FIEMAP_EXTENT_LAST;
} else {
cache.flags |= FIEMAP_EXTENT_LAST;
}
}
out_unlock:
unlock_extent(&inode->io_tree, range_start, range_end, &cached_state);
if (ret == BTRFS_FIEMAP_FLUSH_CACHE) {
btrfs_release_path(path);
ret = flush_fiemap_cache(fieinfo, &cache);
if (ret)
goto out;
len -= cache.next_search_offset - start;
start = cache.next_search_offset;
goto restart;
} else if (ret < 0) {
goto out;
}
/*
* Must free the path before emitting to the fiemap buffer because we
* may have a non-cloned leaf and if the fiemap buffer is memory mapped
* to a file, a write into it (through btrfs_page_mkwrite()) may trigger
* waiting for an ordered extent that in order to complete needs to
* modify that leaf, therefore leading to a deadlock.
*/
btrfs_free_path(path);
path = NULL;
ret = flush_fiemap_cache(fieinfo, &cache);
if (ret)
goto out;
ret = emit_last_fiemap_cache(fieinfo, &cache);
out:
free_extent_state(delalloc_cached_state);
kfree(cache.entries);
btrfs_free_backref_share_ctx(backref_ctx);
btrfs_free_path(path);
return ret;
}
int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
int ret;
ret = fiemap_prep(inode, fieinfo, start, &len, 0);
if (ret)
return ret;
/*
* fiemap_prep() called filemap_write_and_wait() for the whole possible
* file range (0 to LLONG_MAX), but that is not enough if we have
* compression enabled. The first filemap_fdatawrite_range() only kicks
* in the compression of data (in an async thread) and will return
* before the compression is done and writeback is started. A second
* filemap_fdatawrite_range() is needed to wait for the compression to
* complete and writeback to start. We also need to wait for ordered
* extents to complete, because our fiemap implementation uses mainly
* file extent items to list the extents, searching for extent maps
* only for file ranges with holes or prealloc extents to figure out
* if we have delalloc in those ranges.
*/
if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
if (ret)
return ret;
}
btrfs_inode_lock(btrfs_inode, BTRFS_ILOCK_SHARED);
/*
* We did an initial flush to avoid holding the inode's lock while
* triggering writeback and waiting for the completion of IO and ordered
* extents. Now after we locked the inode we do it again, because it's
* possible a new write may have happened in between those two steps.
*/
if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
if (ret) {
btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
return ret;
}
}
ret = extent_fiemap(btrfs_inode, fieinfo, start, len);
btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
return ret;
}

11
fs/btrfs/fiemap.h Normal file
View File

@ -0,0 +1,11 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BTRFS_FIEMAP_H
#define BTRFS_FIEMAP_H
#include <linux/fiemap.h>
int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len);
#endif /* BTRFS_FIEMAP_H */

52
fs/btrfs/inode.c
View File

@ -70,6 +70,7 @@
#include "orphan.h"
#include "backref.h"
#include "raid-stripe-tree.h"
#include "fiemap.h"
struct btrfs_iget_args {
u64 ino;
@ -7929,57 +7930,6 @@ struct iomap_dio *btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter,
IOMAP_DIO_PARTIAL, &data, done_before);
}
static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
int ret;
ret = fiemap_prep(inode, fieinfo, start, &len, 0);
if (ret)
return ret;
/*
* fiemap_prep() called filemap_write_and_wait() for the whole possible
* file range (0 to LLONG_MAX), but that is not enough if we have
* compression enabled. The first filemap_fdatawrite_range() only kicks
* in the compression of data (in an async thread) and will return
* before the compression is done and writeback is started. A second
* filemap_fdatawrite_range() is needed to wait for the compression to
* complete and writeback to start. We also need to wait for ordered
* extents to complete, because our fiemap implementation uses mainly
* file extent items to list the extents, searching for extent maps
* only for file ranges with holes or prealloc extents to figure out
* if we have delalloc in those ranges.
*/
if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
if (ret)
return ret;
}
btrfs_inode_lock(btrfs_inode, BTRFS_ILOCK_SHARED);
/*
* We did an initial flush to avoid holding the inode's lock while
* triggering writeback and waiting for the completion of IO and ordered
* extents. Now after we locked the inode we do it again, because it's
* possible a new write may have happened in between those two steps.
*/
if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
if (ret) {
btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
return ret;
}
}
ret = extent_fiemap(btrfs_inode, fieinfo, start, len);
btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
return ret;
}
/*
* For release_folio() and invalidate_folio() we have a race window where
* folio_end_writeback() is called but the subpage spinlock is not yet released.