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ceph: handle racing calls to ceph_init_dentry

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The ->lookup() and prepopulate_readdir() callers are working with unhashed
dentries, so we don't have to worry.  The export.c callers, though, need
to initialize something they got back from d_obtain_alias() and are
potentially racing with other callers.  Make sure we don't return unless
the dentry is properly initialized (by us or someone else).

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Reviewed-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2011-07-26 11:30:15 -07:00
parent dfabbed6fd
commit 48d0cbd124
1 changed files with 12 additions and 9 deletions
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21
fs/ceph/dir.c
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@ -40,14 +40,6 @@ int ceph_init_dentry(struct dentry *dentry)
if (dentry->d_fsdata)
return 0;
if (dentry->d_parent == NULL || /* nfs fh_to_dentry */
ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
d_set_d_op(dentry, &ceph_dentry_ops);
else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
else
d_set_d_op(dentry, &ceph_snap_dentry_ops);
di = kmem_cache_alloc(ceph_dentry_cachep, GFP_NOFS | __GFP_ZERO);
if (!di)
return -ENOMEM; /* oh well */
@ -58,10 +50,21 @@ int ceph_init_dentry(struct dentry *dentry)
kmem_cache_free(ceph_dentry_cachep, di);
goto out_unlock;
}
if (dentry->d_parent == NULL || /* nfs fh_to_dentry */
ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
d_set_d_op(dentry, &ceph_dentry_ops);
else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
else
d_set_d_op(dentry, &ceph_snap_dentry_ops);
di->dentry = dentry;
di->lease_session = NULL;
dentry->d_fsdata = di;
dentry->d_time = jiffies;
/* avoid reordering d_fsdata setup so that the check above is safe */
smp_mb();
dentry->d_fsdata = di;
ceph_dentry_lru_add(dentry);
out_unlock:
spin_unlock(&dentry->d_lock);