The branch main has been updated by jah:
URL:
https://cgit.FreeBSD.org/src/commit/?id=9530182e371dee382b76d8594f65633a304b396f
commit 9530182e371dee382b76d8594f65633a304b396f
Author: Jason A. Harmening <j...@freebsd.org>
AuthorDate: 2023-12-26 02:02:25 +0000
Commit: Jason A. Harmening <j...@freebsd.org>
CommitDate: 2024-02-18 15:16:16 +0000
VFS: update VOP_FSYNC() debug check to reflect actual locking policy
Shared vs. exclusive locking is determined not by MNT_EXTENDED_SHARED
but by MNT_SHARED_WRITES (although there are several places that
ignore this and simply always use an exclusive lock). Also add a
comment on the possible difference between VOP_GETWRITEMOUNT(vp)
and vp->v_mount on this path.
Found by local testing of unionfs atop ZFS with DEBUG_VFS_LOCKS.
MFC after: 2 weeks
Reviewed by: kib, olce
Differential Revision: https://reviews.freebsd.org/D43816
---
sys/kern/vfs_subr.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 20e220135b15..8f0b00a87cb5 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -5830,7 +5830,22 @@ vop_fsync_debugprepost(struct vnode *vp, const char
*name)
{
if (vp->v_type == VCHR)
;
- else if (MNT_EXTENDED_SHARED(vp->v_mount))
+ /*
+ * The shared vs. exclusive locking policy for fsync()
+ * is actually determined by vp's write mount as indicated
+ * by VOP_GETWRITEMOUNT(), which for stacked filesystems
+ * may not be the same as vp->v_mount. However, if the
+ * underlying filesystem which really handles the fsync()
+ * supports shared locking, the stacked filesystem must also
+ * be prepared for its VOP_FSYNC() operation to be called
+ * with only a shared lock. On the other hand, if the
+ * stacked filesystem claims support for shared write
+ * locking but the underlying filesystem does not, and the
+ * caller incorrectly uses a shared lock, this condition
+ * should still be caught when the stacked filesystem
+ * invokes VOP_FSYNC() on the underlying filesystem.
+ */
+ else if (MNT_SHARED_WRITES(vp->v_mount))
ASSERT_VOP_LOCKED(vp, name);
else
ASSERT_VOP_ELOCKED(vp, name);
