Author: kib
Date: Sun Nov 27 09:10:33 2016
New Revision: 309207
URL: https://svnweb.freebsd.org/changeset/base/309207
Log:
MFC r308618:
Provide simple mutual exclusion between mount point update and unmount.
In the update path in ffs_mount(), drop vfs_busy() reference around namei().
Modified:
stable/11/sys/kern/vfs_mount.c
stable/11/sys/ufs/ffs/ffs_vfsops.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/kern/vfs_mount.c
==============================================================================
--- stable/11/sys/kern/vfs_mount.c Sun Nov 27 05:59:17 2016
(r309206)
+++ stable/11/sys/kern/vfs_mount.c Sun Nov 27 09:10:33 2016
(r309207)
@@ -934,6 +934,11 @@ vfs_domount_update(
VOP_UNLOCK(vp, 0);
MNT_ILOCK(mp);
+ if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0) {
+ MNT_IUNLOCK(mp);
+ error = EBUSY;
+ goto end;
+ }
mp->mnt_flag &= ~MNT_UPDATEMASK;
mp->mnt_flag |= fsflags & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE |
MNT_SNAPSHOT | MNT_ROOTFS | MNT_UPDATEMASK | MNT_RDONLY);
@@ -1293,6 +1298,7 @@ dounmount(struct mount *mp, int flags, s
vn_start_write(NULL, &mp, V_WAIT | V_MNTREF);
MNT_ILOCK(mp);
if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0 ||
+ (mp->mnt_flag & MNT_UPDATE) != 0 ||
!TAILQ_EMPTY(&mp->mnt_uppers)) {
dounmount_cleanup(mp, coveredvp, 0);
return (EBUSY);
Modified: stable/11/sys/ufs/ffs/ffs_vfsops.c
==============================================================================
--- stable/11/sys/ufs/ffs/ffs_vfsops.c Sun Nov 27 05:59:17 2016
(r309206)
+++ stable/11/sys/ufs/ffs/ffs_vfsops.c Sun Nov 27 09:10:33 2016
(r309207)
@@ -147,7 +147,7 @@ ffs_mount(struct mount *mp)
struct ufsmount *ump = NULL;
struct fs *fs;
pid_t fsckpid = 0;
- int error, flags;
+ int error, error1, flags;
uint64_t mntorflags;
accmode_t accmode;
struct nameidata ndp;
@@ -453,6 +453,11 @@ ffs_mount(struct mount *mp)
*/
if (mp->mnt_flag & MNT_SNAPSHOT)
return (ffs_snapshot(mp, fspec));
+
+ /*
+ * Must not call namei() while owning busy ref.
+ */
+ vfs_unbusy(mp);
}
/*
@@ -460,7 +465,18 @@ ffs_mount(struct mount *mp)
* and verify that it refers to a sensible disk device.
*/
NDINIT(&ndp, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, fspec, td);
- if ((error = namei(&ndp)) != 0)
+ error = namei(&ndp);
+ if ((mp->mnt_flag & MNT_UPDATE) != 0) {
+ /*
+ * Unmount does not start if MNT_UPDATE is set. Mount
+ * update busies mp before setting MNT_UPDATE. We
+ * must be able to retain our busy ref succesfully,
+ * without sleep.
+ */
+ error1 = vfs_busy(mp, MBF_NOWAIT);
+ MPASS(error1 == 0);
+ }
+ if (error != 0)
return (error);
NDFREE(&ndp, NDF_ONLY_PNBUF);
devvp = ndp.ni_vp;
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