git: 5adc7b1c9141 - stable/15 - vfs_busy(): add MBF_PCATCH flag to allow interrupting the sleep

The branch stable/15 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=5adc7b1c9141cd002d5b3864c707530a5cce52f1

commit 5adc7b1c9141cd002d5b3864c707530a5cce52f1
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-07-27 13:40:23 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-08-05 06:12:48 +0000

    vfs_busy(): add MBF_PCATCH flag to allow interrupting the sleep
    
    (cherry picked from commit fb4d7bd4b7676963f9f37ff47f315f8c3652538b)
---
 sys/kern/vfs_subr.c | 17 ++++++++++++++++-
 sys/sys/mount.h     |  3 ++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 00795bdd08e7..0e3376929cdb 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -875,6 +875,7 @@ int
 vfs_busy(struct mount *mp, int flags)
 {
 	struct mount_pcpu *mpcpu;
+	int error;
 
 	MPASS((flags & ~MBF_MASK) == 0);
 	CTR3(KTR_VFS, "%s: mp %p with flags %d", __func__, mp, flags);
@@ -919,10 +920,24 @@ vfs_busy(struct mount *mp, int flags)
 		if (flags & MBF_MNTLSTLOCK)
 			mtx_unlock(&mountlist_mtx);
 		mp->mnt_kern_flag |= MNTK_MWAIT;
-		msleep(mp, MNT_MTX(mp), PVFS | PDROP, "vfs_busy", 0);
+		error = msleep(mp, MNT_MTX(mp), ((flags & MBF_PCATCH) != 0 ?
+		    PCATCH : 0) | PVFS | PDROP, "vfs_busy", 0);
 		if (flags & MBF_MNTLSTLOCK)
 			mtx_lock(&mountlist_mtx);
 		MNT_ILOCK(mp);
+		if (error != 0) {
+			MNT_REL(mp);
+
+			/*
+			 * Clearing MNTK_MWAIT might cause spurious
+			 * wakeups, but better clear our flag there
+			 * then leak it.
+			 */
+			mp->mnt_kern_flag &= ~MNTK_MWAIT;
+			wakeup(mp);
+			MNT_IUNLOCK(mp);
+			return (error);
+		}
 	}
 	if (flags & MBF_MNTLSTLOCK)
 		mtx_unlock(&mountlist_mtx);
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index a1e5e4efd460..8636443226e7 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -768,7 +768,8 @@ struct uio;
  */
 #define	MBF_NOWAIT	0x01
 #define	MBF_MNTLSTLOCK	0x02
-#define	MBF_MASK	(MBF_NOWAIT | MBF_MNTLSTLOCK)
+#define	MBF_PCATCH	0x04
+#define	MBF_MASK	(MBF_NOWAIT | MBF_MNTLSTLOCK | MBF_PCATCH)
 
 #ifdef MALLOC_DECLARE
 MALLOC_DECLARE(M_MOUNT);