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btrfs: fix off-by-one end related to inode_need_compress()

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In most cases btrfs uses @end as the inclusive end bytenr for a range,
and this applies to inode_need_compress().

However we have several sites not following the inclusive bytenr:

- run_delalloc_inline()
  Which assigned @blocksize as @end for inode_need_compress()

  This makes inode_need_compress() always skip the disk_i_size check.

- heuristic_collect_sample()
  Which assigned "start + BTRFS_MAX_UNCOMPRESSED" to @end, which is
  the exclusive bytenr.

Neither is really causing any real problem, as
heuristic_collect_sample() has proper checks to avoid reading anything
beyond @end, and the sampling read size is 16 bytes, so it has enough
headroom to handle that off-by-one problem.

But still I do not like anything out of the common scheme, so fix the
off-by-one @end for both call sites, and add extra ASSERT()s to catch
such unaligned parameters.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2026-09-10 11:35:52 +09:30 committed by David Sterba
parent 5a593fe11e
commit 44edf5160b
2 changed files with 11 additions and 9 deletions
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15
fs/btrfs/compression.c
View File

@ -1488,11 +1488,14 @@ static bool sample_repeated_patterns(struct heuristic_ws *ws)
static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
struct heuristic_ws *ws)
{
const u32 blocksize = BTRFS_I(inode)->root->fs_info->sectorsize;
struct folio *folio;
u64 index, index_end;
u32 i, curr_sample_pos;
u8 *in_data;
ASSERT(IS_ALIGNED(start, blocksize) && IS_ALIGNED(end + 1, blocksize));
/*
* Compression handles the input data by chunks of 128KiB
* (defined by BTRFS_MAX_UNCOMPRESSED)
@ -1502,18 +1505,14 @@ static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
* MAX_SAMPLE_SIZE - calculated under assumption that heuristic will
* process no more than BTRFS_MAX_UNCOMPRESSED at a time.
*/
if (end - start > BTRFS_MAX_UNCOMPRESSED)
end = start + BTRFS_MAX_UNCOMPRESSED;
if (end + 1 - start > BTRFS_MAX_UNCOMPRESSED)
end = start + BTRFS_MAX_UNCOMPRESSED - 1;
index = start >> PAGE_SHIFT;
index_end = end >> PAGE_SHIFT;
/* Don't miss unaligned end */
if (!PAGE_ALIGNED(end))
index_end++;
curr_sample_pos = 0;
while (index < index_end) {
while (index <= index_end) {
folio = filemap_get_folio(inode->i_mapping, index);
ASSERT(!IS_ERR(folio));
in_data = kmap_local_folio(folio,
@ -1522,7 +1521,7 @@ static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
i = start % PAGE_SIZE;
while (i < PAGE_SIZE - SAMPLING_READ_SIZE) {
/* Don't sample any garbage from the last page */
if (start > end - SAMPLING_READ_SIZE)
if (start > end + 1 - SAMPLING_READ_SIZE)
break;
memcpy(&ws->sample[curr_sample_pos], &in_data[i],
SAMPLING_READ_SIZE);

5
fs/btrfs/inode.c
View File

@ -730,6 +730,9 @@ static inline int inode_need_compress(struct btrfs_inode *inode, u64 start,
u64 end, bool check_inline)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
const u32 blocksize = fs_info->sectorsize;
ASSERT(IS_ALIGNED(start, blocksize) && IS_ALIGNED(end + 1, blocksize));
if (unlikely(!btrfs_inode_can_compress(inode))) {
DEBUG_WARN("BTRFS: unexpected compression for ino %llu", btrfs_ino(inode));
@ -2331,7 +2334,7 @@ static int run_delalloc_inline(struct btrfs_inode *inode, struct folio *locked_f
btrfs_check_folio_write_protected(locked_folio);
if (btrfs_inode_can_compress(inode) &&
inode_need_compress(inode, 0, blocksize, true)) {
inode_need_compress(inode, 0, blocksize - 1, true)) {
if (inode->defrag_compress > 0 &&
inode->defrag_compress < BTRFS_NR_COMPRESS_TYPES) {
compress_type = inode->defrag_compress;