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Harmening" Subject: git: 9530182e371d - main - VFS: update VOP_FSYNC() debug check to reflect actual locking policy List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-all@freebsd.org X-BeenThere: dev-commits-src-all@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: jah X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 9530182e371dee382b76d8594f65633a304b396f Auto-Submitted: auto-generated The branch main has been updated by jah: URL: https://cgit.FreeBSD.org/src/commit/?id=9530182e371dee382b76d8594f65633a304b396f commit 9530182e371dee382b76d8594f65633a304b396f Author: Jason A. Harmening AuthorDate: 2023-12-26 02:02:25 +0000 Commit: Jason A. Harmening 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);