From af0ed569d7019f1b49e9e51e77b47092e656b00e Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Tue, 26 Jul 2011 11:26:31 -0700 Subject: [PATCH] ceph: fix snap writeback when racing with writes There are two problems that come up when we try to queue a capsnap while a write is in progress: - The FILE_WR cap is held, but not yet dirty, so we may queue a capsnap with dirty == 0. That will crash later in __ceph_flush_snaps(). Or on the FILE_WR cap if a write is in progress. - We may not have i_head_snapc set, which causes problems pretty quickly. Look to the snaprealm in this case. Reviewed-by: Yehuda Sadeh Signed-off-by: Sage Weil --- fs/ceph/snap.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index 54b14de..ac030c9 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -449,6 +449,15 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) spin_lock(&inode->i_lock); used = __ceph_caps_used(ci); dirty = __ceph_caps_dirty(ci); + + /* + * If there is a write in progress, treat that as a dirty Fw, + * even though it hasn't completed yet; by the time we finish + * up this capsnap it will be. + */ + if (used & CEPH_CAP_FILE_WR) + dirty |= CEPH_CAP_FILE_WR; + if (__ceph_have_pending_cap_snap(ci)) { /* there is no point in queuing multiple "pending" cap_snaps, as no new writes are allowed to start when pending, so any @@ -456,14 +465,22 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) cap_snap. lucky us. */ dout("queue_cap_snap %p already pending\n", inode); kfree(capsnap); - } else if (ci->i_wrbuffer_ref_head || (used & CEPH_CAP_FILE_WR) || + } else if (ci->i_wrbuffer_ref_head || (dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL| CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR))) { struct ceph_snap_context *snapc = ci->i_head_snapc; - dout("queue_cap_snap %p cap_snap %p queuing under %p\n", inode, - capsnap, snapc); + /* + * if we are a sync write, we may need to go to the snaprealm + * to get the current snapc. + */ + if (!snapc) + snapc = ci->i_snap_realm->cached_context; + + dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n", + inode, capsnap, snapc, ceph_cap_string(dirty)); ihold(inode); + BUG_ON(dirty == 0); atomic_set(&capsnap->nref, 1); capsnap->ci = ci; -- 2.7.4