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The recent NFS forced unmount improvements introduced a side-effect

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where some client operations might be unexpectedly cancelled during
an unsuccessful non-forced unmount attempt. This causes problems
for amd(8), because it periodically attempts a non-forced unmount
to check if the filesystem is still in use.

Fix this by adding a new mountpoint flag MNTK_UNMOUNTF that is set
only during the operation of a forced unmount. Use this instead of
MNTK_UNMOUNT to trigger the cancellation of hung NFS operations.

Also correct a problem where dounmount() might inadvertently clear
the MNTK_UNMOUNT flag.

Reported by:	simokawa
MFC after:	1 week
This commit is contained in:
Ian Dowse 2002-04-17 01:07:29 +00:00
parent 47d25c1dca
commit df99ca52f1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=94903
4 changed files with 28 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
sys/kern/vfs_extattr.c
View File

@ -1103,11 +1103,18 @@ dounmount(mp, flags, td)
int async_flag;
mtx_lock(&mountlist_mtx);
if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
mtx_unlock(&mountlist_mtx);
return (EBUSY);
}
mp->mnt_kern_flag |= MNTK_UNMOUNT;
/* Allow filesystems to detect that a forced unmount is in progress. */
if (flags & MNT_FORCE)
mp->mnt_kern_flag |= MNTK_UNMOUNTF;
error = lockmgr(&mp->mnt_lock, LK_DRAIN | LK_INTERLOCK |
((flags & MNT_FORCE) ? 0 : LK_NOWAIT), &mountlist_mtx, td);
if (error) {
mp->mnt_kern_flag &= ~MNTK_UNMOUNT;
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
if (mp->mnt_kern_flag & MNTK_MWAIT)
wakeup((caddr_t)mp);
return (error);
@ -1153,7 +1160,7 @@ dounmount(mp, flags, td)
if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL)
(void) vfs_allocate_syncvnode(mp);
mtx_lock(&mountlist_mtx);
mp->mnt_kern_flag &= ~MNTK_UNMOUNT;
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
mp->mnt_flag |= async_flag;
lockmgr(&mp->mnt_lock, LK_RELEASE | LK_INTERLOCK,
&mountlist_mtx, td);

11
sys/kern/vfs_syscalls.c
View File

@ -1103,11 +1103,18 @@ dounmount(mp, flags, td)
int async_flag;
mtx_lock(&mountlist_mtx);
if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
mtx_unlock(&mountlist_mtx);
return (EBUSY);
}
mp->mnt_kern_flag |= MNTK_UNMOUNT;
/* Allow filesystems to detect that a forced unmount is in progress. */
if (flags & MNT_FORCE)
mp->mnt_kern_flag |= MNTK_UNMOUNTF;
error = lockmgr(&mp->mnt_lock, LK_DRAIN | LK_INTERLOCK |
((flags & MNT_FORCE) ? 0 : LK_NOWAIT), &mountlist_mtx, td);
if (error) {
mp->mnt_kern_flag &= ~MNTK_UNMOUNT;
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
if (mp->mnt_kern_flag & MNTK_MWAIT)
wakeup((caddr_t)mp);
return (error);
@ -1153,7 +1160,7 @@ dounmount(mp, flags, td)
if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL)
(void) vfs_allocate_syncvnode(mp);
mtx_lock(&mountlist_mtx);
mp->mnt_kern_flag &= ~MNTK_UNMOUNT;
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
mp->mnt_flag |= async_flag;
lockmgr(&mp->mnt_lock, LK_RELEASE | LK_INTERLOCK,
&mountlist_mtx, td);

8
sys/nfsclient/nfs_socket.c
View File

@ -850,8 +850,8 @@ nfs_request(struct vnode *vp, struct mbuf *mrest, int procnum,
int trylater_delay = NQ_TRYLATERDEL, trylater_cnt = 0;
u_int32_t xid;
/* Reject requests while attempting to unmount. */
if (vp->v_mount->mnt_kern_flag & MNTK_UNMOUNT) {
/* Reject requests while attempting a forced unmount. */
if (vp->v_mount->mnt_kern_flag & MNTK_UNMOUNTF) {
m_freem(mrest);
return (ESTALE);
}
@ -1230,8 +1230,8 @@ nfs_sigintr(struct nfsmount *nmp, struct nfsreq *rep, struct proc *p)
if (rep && (rep->r_flags & R_SOFTTERM))
return (EINTR);
/* Terminate all requests while attempting to unmount. */
if (nmp->nm_mountp->mnt_kern_flag & MNTK_UNMOUNT)
/* Terminate all requests while attempting a forced unmount. */
if (nmp->nm_mountp->mnt_kern_flag & MNTK_UNMOUNTF)
return (EINTR);
if (!(nmp->nm_flag & NFSMNT_INT))
return (0);

6
sys/sys/mount.h
View File

@ -240,7 +240,13 @@ struct mount {
* MNTK_UNMOUNT locks the mount entry so that name lookup cannot proceed
* past the mount point. This keeps the subtree stable during mounts
* and unmounts.
*
* MNTK_UNMOUNTF permits filesystems to detect a forced unmount while
* dounmount() is still waiting to lock the mountpoint. This allows
* the filesystem to cancel operations that might otherwise deadlock
* with the unmount attempt (used by NFS).
*/
#define MNTK_UNMOUNTF 0x00000001 /* forced unmount in progress */
#define MNTK_UNMOUNT 0x01000000 /* unmount in progress */
#define MNTK_MWAIT 0x02000000 /* waiting for unmount to finish */
#define MNTK_WANTRDWR 0x04000000 /* upgrade to read/write requested */