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Forced dismounts of NFS mounts can fail when thread(s) are stuck

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waiting for an RPC reply from the server while holding the mount
point busy (mnt_lockref incremented). This happens because dounmount()
msleep()s waiting for mnt_lockref to become 0, before calling
VFS_UNMOUNT(). This patch adds a new VFS operation called VFS_PURGE(),
which the NFS client implements as purging RPCs in progress. Making
this call before checking mnt_lockref fixes the problem, by ensuring
that the VOP_xxx() calls will fail and unbusy the mount point.

Reported by:	sbruno
Reviewed by:	kib
MFC after:	2 weeks
This commit is contained in:
Rick Macklem 2013-09-01 23:02:59 +00:00
parent 17df25c41c
commit 8fe6bddff7
3 changed files with 34 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
sys/fs/nfsclient/nfs_clvfsops.c
View File

@ -120,6 +120,7 @@ static vfs_root_t nfs_root;
static vfs_statfs_t nfs_statfs;
static vfs_sync_t nfs_sync;
static vfs_sysctl_t nfs_sysctl;
static vfs_purge_t nfs_purge;
/*
* nfs vfs operations.
@ -134,6 +135,7 @@ static struct vfsops nfs_vfsops = {
.vfs_uninit = ncl_uninit,
.vfs_unmount = nfs_unmount,
.vfs_sysctl = nfs_sysctl,
.vfs_purge = nfs_purge,
};
VFS_SET(nfs_vfsops, nfs, VFCF_NETWORK | VFCF_SBDRY);
@ -1675,6 +1677,19 @@ nfs_sysctl(struct mount *mp, fsctlop_t op, struct sysctl_req *req)
return (0);
}
/*
* Purge any RPCs in progress, so that they will all return errors.
* This allows dounmount() to continue as far as VFS_UNMOUNT() for a
* forced dismount.
*/
static void
nfs_purge(struct mount *mp)
{
struct nfsmount *nmp = VFSTONFS(mp);
newnfs_nmcancelreqs(nmp);
}
/*
* Extract the information needed by the nlm from the nfs vnode.
*/

10
sys/kern/vfs_mount.c
View File

@ -1269,8 +1269,16 @@ dounmount(mp, flags, td)
}
mp->mnt_kern_flag |= MNTK_UNMOUNT | MNTK_NOINSMNTQ;
/* Allow filesystems to detect that a forced unmount is in progress. */
if (flags & MNT_FORCE)
if (flags & MNT_FORCE) {
mp->mnt_kern_flag |= MNTK_UNMOUNTF;
MNT_IUNLOCK(mp);
/*
* Must be done after setting MNTK_UNMOUNTF and before
* waiting for mnt_lockref to become 0.
*/
VFS_PURGE(mp);
MNT_ILOCK(mp);
}
error = 0;
if (mp->mnt_lockref) {
mp->mnt_kern_flag |= MNTK_DRAINING;

10
sys/sys/mount.h
View File

@ -609,6 +609,7 @@ typedef int vfs_sysctl_t(struct mount *mp, fsctlop_t op,
struct sysctl_req *req);
typedef void vfs_susp_clean_t(struct mount *mp);
typedef void vfs_notify_lowervp_t(struct mount *mp, struct vnode *lowervp);
typedef void vfs_purge_t(struct mount *mp);
struct vfsops {
vfs_mount_t *vfs_mount;
@ -628,6 +629,7 @@ struct vfsops {
vfs_susp_clean_t *vfs_susp_clean;
vfs_notify_lowervp_t *vfs_reclaim_lowervp;
vfs_notify_lowervp_t *vfs_unlink_lowervp;
vfs_purge_t *vfs_purge;
vfs_mount_t *vfs_spare[6]; /* spares for ABI compat */
};
@ -757,6 +759,14 @@ vfs_statfs_t __vfs_statfs;
} \
} while (0)
#define VFS_PURGE(MP) do { \
if (*(MP)->mnt_op->vfs_purge != NULL) { \
VFS_PROLOGUE(MP); \
(*(MP)->mnt_op->vfs_purge)(MP); \
VFS_EPILOGUE(MP); \
} \
} while (0)
#define VFS_KNOTE_LOCKED(vp, hint) do \
{ \
if (((vp)->v_vflag & VV_NOKNOTE) == 0) \