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ceph: allow dentry_lease_is_valid to work under RCU walk 

Under rcuwalk, we need to take extra care when dereferencing d_parent.
We want to do that once and pass a pointer to dentry_lease_is_valid.

Also, we must ensure that that function can handle the case where we're
racing with d_release. Check whether "di" is NULL under the d_lock, and
just return 0 if so.

Finally, we still need to kick off a renewal job if the lease is getting
close to expiration. If that's the case, then just drop out of rcuwalk
mode since that could block.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>
This commit is contained in:
Jeff Layton 2016-07-01 09:39:20 -04:00 committed by Ilya Dryomov
parent 5b484a5131
commit 14fb9c9efe
1 changed files with 26 additions and 15 deletions
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41
fs/ceph/dir.c
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@ -1133,7 +1133,8 @@ void ceph_invalidate_dentry_lease(struct dentry *dentry)
* Check if dentry lease is valid. If not, delete the lease. Try to
* renew if the least is more than half up.
*/
static int dentry_lease_is_valid(struct dentry *dentry)
static int dentry_lease_is_valid(struct dentry *dentry, unsigned int flags,
struct inode *dir)
{
struct ceph_dentry_info *di;
struct ceph_mds_session *s;
@ -1141,12 +1142,11 @@ static int dentry_lease_is_valid(struct dentry *dentry)
u32 gen;
unsigned long ttl;
struct ceph_mds_session *session = NULL;
struct inode *dir = NULL;
u32 seq = 0;
spin_lock(&dentry->d_lock);
di = ceph_dentry(dentry);
if (di->lease_session) {
if (di && di->lease_session) {
s = di->lease_session;
spin_lock(&s->s_gen_ttl_lock);
gen = s->s_cap_gen;
@ -1159,12 +1159,19 @@ static int dentry_lease_is_valid(struct dentry *dentry)
valid = 1;
if (di->lease_renew_after &&
time_after(jiffies, di->lease_renew_after)) {
/* we should renew */
dir = d_inode(dentry->d_parent);
session = ceph_get_mds_session(s);
seq = di->lease_seq;
di->lease_renew_after = 0;
di->lease_renew_from = jiffies;
/*
* We should renew. If we're in RCU walk mode
* though, we can't do that so just return
* -ECHILD.
*/
if (flags & LOOKUP_RCU) {
valid = -ECHILD;
} else {
session = ceph_get_mds_session(s);
seq = di->lease_seq;
di->lease_renew_after = 0;
di->lease_renew_from = jiffies;
}
}
}
}
@ -1224,12 +1231,16 @@ static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)
} else if (d_really_is_positive(dentry) &&
ceph_snap(d_inode(dentry)) == CEPH_SNAPDIR) {
valid = 1;
} else if (dentry_lease_is_valid(dentry) ||
dir_lease_is_valid(dir, dentry)) {
if (d_really_is_positive(dentry))
valid = ceph_is_any_caps(d_inode(dentry));
else
valid = 1;
} else {
valid = dentry_lease_is_valid(dentry, flags, dir);
if (valid == -ECHILD)
return valid;
if (valid || dir_lease_is_valid(dir, dentry)) {
if (d_really_is_positive(dentry))
valid = ceph_is_any_caps(d_inode(dentry));
else
valid = 1;
}
}
if (!valid) {