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9pfs: fix 'total_open_fd' decrementation

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According to 'man 2 close' errors returned by close() should only be used
for either diagnostic purposes or for catching data loss due to a previous
write error, as an error result of close() usually indicates a deferred
error of a previous write operation.

Therefore not decrementing 'total_open_fd' on a close() error is wrong
and would yield in a higher open file descriptor count than actually the
case, leading to 9p server reclaiming open file descriptors too soon.

Based-on: <20250312152933.383967-7-groug@kaod.org>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <E1tvEyJ-004dMa-So@kylie.crudebyte.com>
This commit is contained in:
Christian Schoenebeck 2025-03-20 13:16:20 +01:00
parent 610dc187e5
commit cdafeda357
3 changed files with 21 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

10
hw/9pfs/9p.c
View file

@ -510,7 +510,15 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
err = (f->fid_type == P9_FID_DIR) ?
s->ops->closedir(&s->ctx, &f->fs_reclaim) :
s->ops->close(&s->ctx, &f->fs_reclaim);
if (!err) {
/* 'man 2 close' suggests to ignore close() errors except of EBADF */
if (unlikely(err && errno == EBADF)) {
/*
* unexpected case as FIDs were picked above by having a valid
* file descriptor
*/
error_report("9pfs: v9fs_reclaim_fd() WARNING: close() failed with EBADF");
} else {
/* total_open_fd must only be mutated on main thread */
nclosed++;
}