Nullfs leaks i-nodes
Goran Lowkrantz
goran.lowkrantz at ismobile.com
Thu May 9 12:11:55 UTC 2013
--On Wednesday, 08 May, 2013 12:13 PM +0300 Konstantin Belousov
<kostikbel at gmail.com> wrote:
> On Tue, May 07, 2013 at 08:30:06AM +0200, G??ran L??wkrantz wrote:
>> I created a PR, kern/178238, on this but would like to know if anyone
>> has any ideas or patches?
>>
>> Have updated the system where I see this to FreeBSD 9.1-STABLE #0
>> r250229 and still have the problem.
>
> The patch below should fix the issue for you, at least it did so in my
> limited testing.
>
> What is does:
> 1. When inactivating a nullfs vnode, check if the lower vnode is
> unlinked, and reclaim upper vnode if so. [This fixes your case].
>
> 2. Besides a callback to the upper filesystems for the lower vnode
> reclaimation, it also calls the upper fs for lower vnode unlink.
> This allows nullfs to purge cached vnodes for the unlinked lower.
> [This fixes an opposite case, when the vnode is removed from the
> lower mount, but upper aliases prevent the vnode from being
> recycled].
>
> 3. Fix a wart which existed from the introduction of the nullfs caching,
> do not unlock lower vnode in the nullfs_reclaim_lowervp(). It should
> be completely innocent, but now it is also formally safe.
>
> 4. Fix vnode reference leak in nullfs_reclaim_lowervp().
>
> Please note that the patch is basically not tested, I only verified your
> scenario and a mirror of it as described in item 2.
>
> diff --git a/sys/fs/nullfs/null.h b/sys/fs/nullfs/null.h
> index 4f37020..a624be6 100644
> --- a/sys/fs/nullfs/null.h
> +++ b/sys/fs/nullfs/null.h
> @@ -53,8 +53,11 @@ struct null_node {
> LIST_ENTRY(null_node) null_hash; /* Hash list */
> struct vnode *null_lowervp; /* VREFed once */
> struct vnode *null_vnode; /* Back pointer */
> + u_int null_flags;
> };
>
> +#define NULLV_NOUNLOCK 0x0001
> +
> #define MOUNTTONULLMOUNT(mp) ((struct null_mount *)((mp)->mnt_data))
> #define VTONULL(vp) ((struct null_node *)(vp)->v_data)
> #define NULLTOV(xp) ((xp)->null_vnode)
> diff --git a/sys/fs/nullfs/null_vfsops.c b/sys/fs/nullfs/null_vfsops.c
> index 02932bd..544c358 100644
> --- a/sys/fs/nullfs/null_vfsops.c
> +++ b/sys/fs/nullfs/null_vfsops.c
> @@ -65,7 +65,6 @@ static vfs_statfs_t nullfs_statfs;
> static vfs_unmount_t nullfs_unmount;
> static vfs_vget_t nullfs_vget;
> static vfs_extattrctl_t nullfs_extattrctl;
> -static vfs_reclaim_lowervp_t nullfs_reclaim_lowervp;
>
> /*
> * Mount null layer
> @@ -391,8 +390,22 @@ nullfs_reclaim_lowervp(struct mount *mp, struct
> vnode *lowervp) vp = null_hashget(mp, lowervp);
> if (vp == NULL)
> return;
> + VTONULL(vp)->null_flags |= NULLV_NOUNLOCK;
> vgone(vp);
> - vn_lock(lowervp, LK_EXCLUSIVE | LK_RETRY);
> + vput(vp);
> +}
> +
> +static void
> +nullfs_unlink_lowervp(struct mount *mp, struct vnode *lowervp)
> +{
> + struct vnode *vp;
> +
> + vp = null_hashget(mp, lowervp);
> + if (vp == NULL || vp->v_usecount > 1)
> + return;
> + VTONULL(vp)->null_flags |= NULLV_NOUNLOCK;
> + vgone(vp);
> + vput(vp);
> }
>
> static struct vfsops null_vfsops = {
> @@ -408,6 +421,7 @@ static struct vfsops null_vfsops = {
> .vfs_unmount = nullfs_unmount,
> .vfs_vget = nullfs_vget,
> .vfs_reclaim_lowervp = nullfs_reclaim_lowervp,
> + .vfs_unlink_lowervp = nullfs_unlink_lowervp,
> };
>
> VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK | VFCF_JAIL);
> diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c
> index f59865f..3c41124 100644
> --- a/sys/fs/nullfs/null_vnops.c
> +++ b/sys/fs/nullfs/null_vnops.c
> @@ -692,18 +692,21 @@ null_unlock(struct vop_unlock_args *ap)
> static int
> null_inactive(struct vop_inactive_args *ap __unused)
> {
> - struct vnode *vp;
> + struct vnode *vp, *lvp;
> struct mount *mp;
> struct null_mount *xmp;
>
> vp = ap->a_vp;
> + lvp = NULLVPTOLOWERVP(vp);
> mp = vp->v_mount;
> xmp = MOUNTTONULLMOUNT(mp);
> - if ((xmp->nullm_flags & NULLM_CACHE) == 0) {
> + if ((xmp->nullm_flags & NULLM_CACHE) == 0 ||
> + (lvp->v_vflag & VV_NOSYNC) != 0) {
> /*
> * If this is the last reference and caching of the
> - * nullfs vnodes is not enabled, then free up the
> - * vnode so as not to tie up the lower vnodes.
> + * nullfs vnodes is not enabled, or the lower vnode is
> + * deleted, then free up the vnode so as not to tie up
> + * the lower vnodes.
> */
> vp->v_object = NULL;
> vrecycle(vp);
> @@ -748,7 +751,10 @@ null_reclaim(struct vop_reclaim_args *ap)
> */
> if (vp->v_writecount > 0)
> VOP_ADD_WRITECOUNT(lowervp, -1);
> - vput(lowervp);
> + if ((xp->null_flags & NULLV_NOUNLOCK) != 0)
> + vunref(lowervp);
> + else
> + vput(lowervp);
> free(xp, M_NULLFSNODE);
>
> return (0);
> diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
> index de118f7..988a114 100644
> --- a/sys/kern/vfs_subr.c
> +++ b/sys/kern/vfs_subr.c
> @@ -2700,19 +2700,20 @@ vgone(struct vnode *vp)
> }
>
> static void
> -vgonel_reclaim_lowervp_vfs(struct mount *mp __unused,
> +notify_lowervp_vfs_dummy(struct mount *mp __unused,
> struct vnode *lowervp __unused)
> {
> }
>
> /*
> - * Notify upper mounts about reclaimed vnode.
> + * Notify upper mounts about reclaimed or unlinked vnode.
> */
> -static void
> -vgonel_reclaim_lowervp(struct vnode *vp)
> +void
> +vfs_notify_upper(struct vnode *vp, int event)
> {
> static struct vfsops vgonel_vfsops = {
> - .vfs_reclaim_lowervp = vgonel_reclaim_lowervp_vfs
> + .vfs_reclaim_lowervp = notify_lowervp_vfs_dummy,
> + .vfs_unlink_lowervp = notify_lowervp_vfs_dummy,
> };
> struct mount *mp, *ump, *mmp;
>
> @@ -2736,7 +2737,17 @@ vgonel_reclaim_lowervp(struct vnode *vp)
> }
> TAILQ_INSERT_AFTER(&mp->mnt_uppers, ump, mmp, mnt_upper_link);
> MNT_IUNLOCK(mp);
> - VFS_RECLAIM_LOWERVP(ump, vp);
> + switch (event) {
> + case VFS_NOTIFY_UPPER_RECLAIM:
> + VFS_RECLAIM_LOWERVP(ump, vp);
> + break;
> + case VFS_NOTIFY_UPPER_UNLINK:
> + VFS_UNLINK_LOWERVP(ump, vp);
> + break;
> + default:
> + KASSERT(0, ("invalid event %d", event));
> + break;
> + }
> MNT_ILOCK(mp);
> ump = TAILQ_NEXT(mmp, mnt_upper_link);
> TAILQ_REMOVE(&mp->mnt_uppers, mmp, mnt_upper_link);
> @@ -2783,7 +2794,7 @@ vgonel(struct vnode *vp)
> active = vp->v_usecount;
> oweinact = (vp->v_iflag & VI_OWEINACT);
> VI_UNLOCK(vp);
> - vgonel_reclaim_lowervp(vp);
> + vfs_notify_upper(vp, VFS_NOTIFY_UPPER_RECLAIM);
>
> /*
> * Clean out any buffers associated with the vnode.
> diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
> index 29cb7bd..a004ea0 100644
> --- a/sys/kern/vfs_syscalls.c
> +++ b/sys/kern/vfs_syscalls.c
> @@ -1846,6 +1846,7 @@ restart:
> if (error)
> goto out;
> #endif
> + vfs_notify_upper(vp, VFS_NOTIFY_UPPER_UNLINK);
> error = VOP_REMOVE(nd.ni_dvp, vp, &nd.ni_cnd);
> #ifdef MAC
> out:
> @@ -3825,6 +3826,7 @@ restart:
> return (error);
> goto restart;
> }
> + vfs_notify_upper(vp, VFS_NOTIFY_UPPER_UNLINK);
> error = VOP_RMDIR(nd.ni_dvp, nd.ni_vp, &nd.ni_cnd);
> vn_finished_write(mp);
> out:
> diff --git a/sys/sys/mount.h b/sys/sys/mount.h
> index a9c86f6..a953dae 100644
> --- a/sys/sys/mount.h
> +++ b/sys/sys/mount.h
> @@ -608,7 +608,7 @@ typedef int vfs_mount_t(struct mount *mp);
> 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_reclaim_lowervp_t(struct mount *mp, struct vnode
> *lowervp); +typedef void vfs_notify_lowervp_t(struct mount *mp, struct
> vnode *lowervp);
> struct vfsops {
> vfs_mount_t *vfs_mount;
> @@ -626,7 +626,8 @@ struct vfsops {
> vfs_extattrctl_t *vfs_extattrctl;
> vfs_sysctl_t *vfs_sysctl;
> vfs_susp_clean_t *vfs_susp_clean;
> - vfs_reclaim_lowervp_t *vfs_reclaim_lowervp;
> + vfs_notify_lowervp_t *vfs_reclaim_lowervp;
> + vfs_notify_lowervp_t *vfs_unlink_lowervp;
> };
>
> vfs_statfs_t __vfs_statfs;
> @@ -747,6 +748,14 @@ vfs_statfs_t __vfs_statfs;
> } \
> } while (0)
>
> +#define VFS_UNLINK_LOWERVP(MP, VP) do { \
> + if (*(MP)->mnt_op->vfs_unlink_lowervp != NULL) { \
> + VFS_PROLOGUE(MP); \
> + (*(MP)->mnt_op->vfs_unlink_lowervp)((MP), (VP)); \
> + VFS_EPILOGUE(MP); \
> + } \
> +} while (0)
> +
> #define VFS_KNOTE_LOCKED(vp, hint) do \
> { \
> if (((vp)->v_vflag & VV_NOKNOTE) == 0) \
> @@ -759,6 +768,9 @@ vfs_statfs_t __vfs_statfs;
> VN_KNOTE((vp), (hint), 0); \
> } while (0)
>
> +#define VFS_NOTIFY_UPPER_RECLAIM 1
> +#define VFS_NOTIFY_UPPER_UNLINK 2
> +
> #include <sys/module.h>
>
> /*
> @@ -840,6 +852,7 @@ int vfs_modevent(module_t, int, void *);
> void vfs_mount_error(struct mount *, const char *, ...);
> void vfs_mountroot(void); /* mount our root filesystem */
> void vfs_mountedfrom(struct mount *, const char *from);
> +void vfs_notify_upper(struct vnode *, int);
> void vfs_oexport_conv(const struct oexport_args *oexp,
> struct export_args *exp);
> void vfs_ref(struct mount *);
I assume this is CURRENT? Tried on STABLE but got this:
cc1: warnings being treated as errors
/usr/src/sys/kern/vfs_subr.c: In function 'vfs_notify_upper':
/usr/src/sys/kern/vfs_subr.c:2801: warning: implicit declaration of
function 'VFS_PROLOGUE'
/usr/src/sys/kern/vfs_subr.c:2801: warning: nested extern declaration of
'VFS_PROLOGUE' [-Wnested-externs]
/usr/src/sys/kern/vfs_subr.c:2801: warning: implicit declaration of
function 'VFS_EPILOGUE'
/usr/src/sys/kern/vfs_subr.c:2801: warning: nested extern declaration of
'VFS_EPILOGUE' [-Wnested-externs]
*** [vfs_subr.o] Error code 1
/glz
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