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xfs: fix finding a last resort AG in xfs_filestream_pick_ag

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When the main loop in xfs_filestream_pick_ag fails to find a suitable
AG it tries to just pick the online AG.  But the loop for that uses
args->pag as loop iterator while the later code expects pag to be
set.  Fix this by reusing the max_pag case for this last resort, and
also add a check for impossible case of no AG just to make sure that
the uninitialized pag doesn't even escape in theory.

Reported-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Fixes: f8f1ed1ab3 ("xfs: return a referenced perag from filestreams allocator")
Cc: <stable@vger.kernel.org> # v6.3
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
This commit is contained in:
Christoph Hellwig 2024-10-23 15:37:22 +02:00 committed by Carlos Maiolino
parent 3ef2268403
commit dc60992ce7
2 changed files with 17 additions and 21 deletions
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23
fs/xfs/xfs_filestream.c
View File

@ -64,7 +64,7 @@ xfs_filestream_pick_ag(
struct xfs_perag *pag;
struct xfs_perag *max_pag = NULL;
xfs_extlen_t minlen = *longest;
xfs_extlen_t free = 0, minfree, maxfree = 0;
xfs_extlen_t minfree, maxfree = 0;
xfs_agnumber_t agno;
bool first_pass = true;
int err;
@ -107,7 +107,6 @@ restart:
!(flags & XFS_PICK_USERDATA) ||
(flags & XFS_PICK_LOWSPACE))) {
/* Break out, retaining the reference on the AG. */
free = pag->pagf_freeblks;
break;
}
}
@ -150,23 +149,25 @@ restart:
* grab.
*/
if (!max_pag) {
for_each_perag_wrap(args->mp, 0, start_agno, args->pag)
for_each_perag_wrap(args->mp, 0, start_agno, pag) {
max_pag = pag;
break;
atomic_inc(&args->pag->pagf_fstrms);
*longest = 0;
} else {
pag = max_pag;
free = maxfree;
atomic_inc(&pag->pagf_fstrms);
}
/* Bail if there are no AGs at all to select from. */
if (!max_pag)
return -ENOSPC;
}
pag = max_pag;
atomic_inc(&pag->pagf_fstrms);
} else if (max_pag) {
xfs_perag_rele(max_pag);
}
trace_xfs_filestream_pick(pag, pino, free);
trace_xfs_filestream_pick(pag, pino);
args->pag = pag;
return 0;
}
static struct xfs_inode *

15
fs/xfs/xfs_trace.h
View File

@ -691,8 +691,8 @@ DEFINE_FILESTREAM_EVENT(xfs_filestream_lookup);
DEFINE_FILESTREAM_EVENT(xfs_filestream_scan);
TRACE_EVENT(xfs_filestream_pick,
TP_PROTO(struct xfs_perag *pag, xfs_ino_t ino, xfs_extlen_t free),
TP_ARGS(pag, ino, free),
TP_PROTO(struct xfs_perag *pag, xfs_ino_t ino),
TP_ARGS(pag, ino),
TP_STRUCT__entry(
__field(dev_t, dev)
__field(xfs_ino_t, ino)
@ -703,14 +703,9 @@ TRACE_EVENT(xfs_filestream_pick,
TP_fast_assign(
__entry->dev = pag->pag_mount->m_super->s_dev;
__entry->ino = ino;
if (pag) {
__entry->agno = pag->pag_agno;
__entry->streams = atomic_read(&pag->pagf_fstrms);
} else {
__entry->agno = NULLAGNUMBER;
__entry->streams = 0;
}
__entry->free = free;
__entry->agno = pag->pag_agno;
__entry->streams = atomic_read(&pag->pagf_fstrms);
__entry->free = pag->pagf_freeblks;
),
TP_printk("dev %d:%d ino 0x%llx agno 0x%x streams %d free %d",
MAJOR(__entry->dev), MINOR(__entry->dev),