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btrfs: remove the free space inode special cases from the COW paths

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Free space inodes are never written anymore, so drop the special cases
for them in cow_file_range(), fallback_to_cow(),
can_nocow_file_extent() and btrfs_finish_one_ordered().

Assisted-by: LLM
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Tal Zussman 2026-10-15 10:43:29 -04:00 committed by David Sterba
parent d6c5cf6c58
commit 557a72b63a
1 changed files with 14 additions and 40 deletions
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54
fs/btrfs/inode.c
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@ -1369,11 +1369,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
goto out_unlock;
}
if (btrfs_is_free_space_inode(inode)) {
ret = -EINVAL;
goto out_unlock;
}
num_bytes = ALIGN(end - start + 1, blocksize);
num_bytes = max(blocksize, num_bytes);
ASSERT(num_bytes <= btrfs_super_total_bytes(fs_info->super_copy));
@ -1683,7 +1678,6 @@ static int fallback_to_cow(struct btrfs_inode *inode,
struct folio *locked_folio, const u64 start,
const u64 end)
{
const bool is_space_ino = btrfs_is_free_space_inode(inode);
const bool is_reloc_ino = btrfs_is_data_reloc_root(inode->root);
const u64 range_bytes = end + 1 - start;
struct extent_io_tree *io_tree = &inode->io_tree;
@ -1716,23 +1710,22 @@ static int fallback_to_cow(struct btrfs_inode *inode,
* extent_clear_unlock_delalloc()) the bytes_may_use counter of the
* data space info, which we incremented in the step above.
*
* If we need to fallback to cow and the inode corresponds to a free
* space cache inode or an inode of the data relocation tree, we must
* also increment bytes_may_use of the data space_info for the same
* reason. Space caches and relocated data extents always get a prealloc
* extent for them, however scrub or balance may have set the block
* group that contains that extent to RO mode and therefore force COW
* when starting writeback.
* If we need to fallback to cow and the inode is in the data relocation
* tree, we must also increment bytes_may_use of the data space_info for
* the same reason. Relocated data extents always get a prealloc extent,
* however scrub or balance may have set the block group that contains
* that extent to RO mode and therefore force COW when starting
* writeback.
*/
btrfs_lock_extent(io_tree, start, end, &cached_state);
count = btrfs_count_range_bits(io_tree, &range_start, end, range_bytes,
EXTENT_NORESERVE, false, NULL);
if (count > 0 || is_space_ino || is_reloc_ino) {
if (count > 0 || is_reloc_ino) {
u64 bytes = count;
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct btrfs_space_info *sinfo = fs_info->data_sinfo;
if (is_space_ino || is_reloc_ino)
if (is_reloc_ino)
bytes = range_bytes;
spin_lock(&sinfo->lock);
@ -1797,7 +1790,6 @@ static int can_nocow_file_extent(struct btrfs_path *path,
struct btrfs_inode *inode,
struct can_nocow_file_extent_args *args)
{
const bool is_freespace_inode = btrfs_is_free_space_inode(inode);
struct extent_buffer *leaf = path->nodes[0];
struct btrfs_root *root = inode->root;
struct btrfs_file_extent_item *fi;
@ -1810,8 +1802,7 @@ static int can_nocow_file_extent(struct btrfs_path *path,
bool nowait = path->nowait;
/* If there are pending snapshots for this root, we must do COW. */
if (args->writeback_path && !is_freespace_inode &&
atomic_read(&root->snapshot_force_cow))
if (args->writeback_path && atomic_read(&root->snapshot_force_cow))
goto out;
fi = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item);
@ -1860,7 +1851,6 @@ static int can_nocow_file_extent(struct btrfs_path *path,
ret = btrfs_cross_ref_exist(inode, key->offset - args->file_extent.offset,
args->file_extent.disk_bytenr, path);
WARN_ON_ONCE(ret > 0 && is_freespace_inode);
if (ret != 0)
goto out;
@ -1895,7 +1885,6 @@ static int can_nocow_file_extent(struct btrfs_path *path,
ret = btrfs_lookup_csums_list(csum_root, io_start,
io_start + args->file_extent.num_bytes - 1,
NULL, nowait);
WARN_ON_ONCE(ret > 0 && is_freespace_inode);
if (ret != 0)
goto out;
@ -3221,6 +3210,7 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
int compress_type = 0;
int ret = 0;
u64 logical_len = ordered_extent->num_bytes;
u64 unwritten_start;
bool truncated = false;
bool clear_reserved_extent = true;
unsigned int clear_bits = 0;
@ -3386,27 +3376,11 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
* Drop extent maps for the part of the extent we didn't write.
* On error the written part is freed below as well, so drop
* its maps too.
*
* We have an exception here for the free_space_inode, this is
* because when we do btrfs_get_extent() on the free space inode
* we will search the commit root. If this is a new block group
* we won't find anything, and we will trip over the assert in
* writepage where we do ASSERT(em->block_start !=
* EXTENT_MAP_HOLE).
*
* Theoretically we could also skip this for any NOCOW extent as
* we don't mess with the extent map tree in the NOCOW case, but
* for now simply skip this if we are the free space inode.
*/
if (!btrfs_is_free_space_inode(inode)) {
u64 unwritten_start = start;
if (truncated && !ret)
unwritten_start += logical_len;
btrfs_drop_extent_map_range(inode, unwritten_start,
end, false);
}
unwritten_start = start;
if (truncated && !ret)
unwritten_start += logical_len;
btrfs_drop_extent_map_range(inode, unwritten_start, end, false);
/*
* If the ordered extent had an IOERR or something else went