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ffs_vput_pair(): try harder to recover from the vnode reclaim

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In particular, if unlock_vp is false, save vp's inode number and
generation. If ffs_inotovp() can re-create the vnode with the same
number and generation after we finished with handling dvp, then we most
likely raced with unmount, and were able to restore atomicity of open.
We use FFSV_REPLACE_DOOMED there, to drop the old vnode.

This additional recovery is not strictly required, but it improves the
quality of the implementation.

Suggested by:	mckusick
Reviewed by:	chs, mckusick
Tested by:	pho
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2021-01-27 20:10:51 +02:00
parent f2c9d038bd
commit 30bfb2fa0f
1 changed files with 36 additions and 3 deletions
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39
sys/ufs/ffs/ffs_vnops.c
View file

@ -1924,8 +1924,11 @@ ffs_getpages_async(struct vop_getpages_async_args *ap)
static int
ffs_vput_pair(struct vop_vput_pair_args *ap)
{
struct vnode *dvp, *vp, **vpp;
struct inode *dp;
struct mount *mp;
struct vnode *dvp, *vp, *vp1, **vpp;
struct inode *dp, *ip;
ino_t ip_ino;
u_int64_t ip_gen;
int error, vp_locked;
dvp = ap->a_dvp;
@ -1940,12 +1943,17 @@ ffs_vput_pair(struct vop_vput_pair_args *ap)
return (0);
}
mp = NULL;
if (vp != NULL) {
if (ap->a_unlock_vp) {
vput(vp);
} else {
MPASS(vp->v_type != VNON);
vp_locked = VOP_ISLOCKED(vp);
ip = VTOI(vp);
ip_ino = ip->i_number;
ip_gen = ip->i_gen;
mp = vp->v_mount;
VOP_UNLOCK(vp);
}
}
@ -1957,6 +1965,7 @@ ffs_vput_pair(struct vop_vput_pair_args *ap)
if (vp == NULL || ap->a_unlock_vp)
return (0);
MPASS(mp != NULL);
/*
* It is possible that vp is reclaimed at this point. Only
@ -1970,5 +1979,29 @@ ffs_vput_pair(struct vop_vput_pair_args *ap)
* and respond to dead vnodes by returning ESTALE.
*/
VOP_LOCK(vp, vp_locked | LK_RETRY);
return (0);
if (!VN_IS_DOOMED(vp))
return (0);
/*
* Try harder to recover from reclaimed vp if reclaim was not
* because underlying inode was cleared. We saved inode
* number and inode generation, so we can try to reinstantiate
* exactly same version of inode. If this fails, return
* original doomed vnode and let caller to handle
* consequences.
*
* Note that callers must keep write started around
* VOP_VPUT_PAIR() calls, so it is safe to use mp without
* busying it.
*/
VOP_UNLOCK(vp);
error = ffs_inotovp(mp, ip_ino, ip_gen, LK_EXCLUSIVE, &vp1,
FFSV_REPLACE_DOOMED);
if (error != 0) {
VOP_LOCK(vp, vp_locked | LK_RETRY);
} else {
vrele(vp);
*vpp = vp1;
}
return (error);
}