ceph: fix flush_dirty_caps race with caps migration
The flush_dirty_caps() used to loop over the first entry of the cap_dirty
dirty list on the assumption that after calling ceph_check_caps() it would
be removed from the list. This isn't true for caps that are being
migrated between MDSs, where we've received the EXPORT but not the IMPORT.
Instead, do a safe list iteration, and pin the next inode on the list via
the CEPH_I_NOFLUSH flag.
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 295b7e54..8b89b91 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1573,6 +1573,11 @@
}
ack:
+ if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
+ dout(" skipping %p I_NOFLUSH set\n", inode);
+ continue;
+ }
+
if (session && session != cap->session) {
dout("oops, wrong session %p mutex\n", session);
mutex_unlock(&session->s_mutex);
@@ -1652,6 +1657,10 @@
retry:
spin_lock(&inode->i_lock);
+ if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
+ dout("try_flush_caps skipping %p I_NOFLUSH set\n", inode);
+ goto out;
+ }
if (ci->i_dirty_caps && ci->i_auth_cap) {
struct ceph_cap *cap = ci->i_auth_cap;
int used = __ceph_caps_used(ci);
@@ -2747,16 +2756,38 @@
*/
void ceph_flush_dirty_caps(struct ceph_mds_client *mdsc)
{
- struct ceph_inode_info *ci;
- struct inode *inode;
+ struct ceph_inode_info *ci, *nci = NULL;
+ struct inode *inode, *ninode = NULL;
+ struct list_head *p, *n;
dout("flush_dirty_caps\n");
spin_lock(&mdsc->cap_dirty_lock);
- while (!list_empty(&mdsc->cap_dirty)) {
- ci = list_first_entry(&mdsc->cap_dirty,
- struct ceph_inode_info,
- i_dirty_item);
- inode = igrab(&ci->vfs_inode);
+ list_for_each_safe(p, n, &mdsc->cap_dirty) {
+ if (nci) {
+ ci = nci;
+ inode = ninode;
+ ci->i_ceph_flags &= ~CEPH_I_NOFLUSH;
+ dout("flush_dirty_caps inode %p (was next inode)\n",
+ inode);
+ } else {
+ ci = list_entry(p, struct ceph_inode_info,
+ i_dirty_item);
+ inode = igrab(&ci->vfs_inode);
+ BUG_ON(!inode);
+ dout("flush_dirty_caps inode %p\n", inode);
+ }
+ if (n != &mdsc->cap_dirty) {
+ nci = list_entry(n, struct ceph_inode_info,
+ i_dirty_item);
+ ninode = igrab(&nci->vfs_inode);
+ BUG_ON(!ninode);
+ nci->i_ceph_flags |= CEPH_I_NOFLUSH;
+ dout("flush_dirty_caps next inode %p, noflush\n",
+ ninode);
+ } else {
+ nci = NULL;
+ ninode = NULL;
+ }
spin_unlock(&mdsc->cap_dirty_lock);
if (inode) {
ceph_check_caps(ci, CHECK_CAPS_NODELAY|CHECK_CAPS_FLUSH,