tree a41ecef92354c88dfc24fc574bde5bce0c71f52b
parent ae3afdde83bfb3b7927ab5457808a13a2ac4c8a1
author Darrick J. Wong <djwong@kernel.org> 1731703715 -0800
committer Darrick J. Wong <djwong@kernel.org> 1731970791 -0800

xfs: fix null bno_hint handling in xfs_rtallocate_rtg

xfs_bmap_rtalloc initializes the bno_hint variable to NULLRTBLOCK (aka
NULLFSBLOCK).  If the allocation request is for a file range that's
adjacent to an existing mapping, it will then change bno_hint to the
blkno hint in the bmalloca structure.

In other words, bno_hint is either a rt block number, or it's all 1s.
Unfortunately, commit ec12f97f1b8a8f didn't take the NULLRTBLOCK state
into account, which means that it tries to translate that into a
realtime extent number.  We then end up with an obnoxiously high rtx
number and pointlessly feed that to the near allocator.  This often
fails and falls back to the by-size allocator.  Seeing as we had no
locality hint anyway, this is a waste of time.

Fix the code to detect a lack of bno_hint correctly.  This was detected
by running xfs/009 with metadir enabled and a 28k rt extent size.

Cc: <stable@vger.kernel.org> # v6.12
Fixes: ec12f97f1b8a8f ("xfs: make the rtalloc start hint a xfs_rtblock_t")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>