Re: [PATCH 1/2] btrfs: use proper inclusive end in extent_fiemap()

On Tue, 28 Jul 2026 at 10:40, Qu Wenruo <[email protected]> wrote:
> 在 2026/7/28 17:35, Daniel Vacek 写道:
> > On Tue, 28 Jul 2026 at 08:46, Qu Wenruo <[email protected]> wrote:
> >> The @end parameter for all extent io tree helpers is inclusive, but
> >> the call site in extent_fiemap() is passing exclusive end.
> >>
> >> Fix it to follow the common pattern.
> >>
> >> Fixes: ac3c0d36a2a2 ("btrfs: make fiemap more efficient and accurate reporting extent sharedness")
> >> Signed-off-by: Qu Wenruo <[email protected]>
> >> ---
> >>   fs/btrfs/fiemap.c | 8 ++++----
> >>   1 file changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/fs/btrfs/fiemap.c b/fs/btrfs/fiemap.c
> >> index ba6a360074c0..2f2ae0b76799 100644
> >> --- a/fs/btrfs/fiemap.c
> >> +++ b/fs/btrfs/fiemap.c
> >> @@ -657,7 +657,7 @@ static int extent_fiemap(struct btrfs_inode *inode,
> >>
> >>   restart:
> >>          range_start = round_down(start, sectorsize);
> >> -       range_end = round_up(start + len, sectorsize);
> >> +       range_end = round_up(start + len, sectorsize) - 1;
> >>          prev_extent_end = range_start;
> >>
> >>          btrfs_lock_extent(&inode->io_tree, range_start, range_end, &cached_state);
> >> @@ -710,7 +710,7 @@ static int extent_fiemap(struct btrfs_inode *inode,
> >>
> >>                  /* 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;
> >> +                       const u64 hole_end = min(key.offset - 1, range_end);
> >>
> >>                          ret = fiemap_process_hole(inode, fieinfo, &cache,
> >>                                                    &delalloc_cached_state,
> >> @@ -812,10 +812,10 @@ static int extent_fiemap(struct btrfs_inode *inode,
> >>          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);
> >> +                                         0, 0, 0, prev_extent_end, range_end);
> >>                  if (ret < 0)
> >>                          goto out_unlock;
> >> -               prev_extent_end = range_end;
> >> +               prev_extent_end = range_end + 1;
> >>          }
> >>
> >>          if (cache.cached && cache.offset + cache.len >= last_extent_end) {
> >> --
> >> 2.54.0
> >
> > I don't really get why you left out these:
> >
> > @@ -680,7 +680,7 @@ static int extent_fiemap(struct btrfs_inode *inode,
> >                  goto check_eof_delalloc;
> >          }
> >
> > -       while (prev_extent_end < range_end) {
> > +       while (prev_extent_end <= range_end) {
> >                  struct extent_buffer *leaf = path->nodes[0];
> >                  struct btrfs_file_extent_item *ei;
> >                  struct btrfs_key key;
> > @@ -809,13 +809,13 @@ static int extent_fiemap(struct btrfs_inode *inode,
> >          }
> >
> >   check_eof_delalloc:
> > -       if (!stopped && prev_extent_end < range_end) {
> > +       if (!stopped && prev_extent_end <= range_end) {
> >                  ret = fiemap_process_hole(inode, fieinfo, &cache,
> >                                            &delalloc_cached_state, backref_ctx,
> >
> > Am I missing something?
>
> Because we won't reach the == case at all.
>
> The start is always increased by a value aligned to sectorsize.

I understand round_down() possibly decreases not increases. So if
start and start + len - 1 fall into the same block you get the ==
case. Am I wrong?

> For inclusive range_end, we either completely pass it by 1, or smaller
> than it.
>
> So that "==" will never be hit.>
> > --nX
>