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ceph: delay umount until all mds requests drop inode+dentry refs

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This fixes a race between handle_reply finishing an mds request, signalling
completion, and then dropping the request structing and its dentry+inode
refs, and pre_umount function waiting for requests to finish before
letting the vfs tear down the dcache.  If umount was delayed waiting for
mds requests, we could race and BUG in shrink_dcache_for_umount_subtree
because of a slow dput.

This delays umount until the msgr queue flushes, which means handle_reply
will exit and will have dropped the ceph_mds_request struct.  I'm assuming
the VFS has already ensured that its calls have all completed and those
request refs have thus been dropped as well (I haven't seen that race, at
least).

Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2010-06-21 16:12:26 -07:00
parent d69ed05a80
commit 17c688c3df
1 changed files with 6 additions and 0 deletions
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6
fs/ceph/mds_client.c
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@ -2783,6 +2783,12 @@ void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
drop_leases(mdsc);
ceph_flush_dirty_caps(mdsc);
wait_requests(mdsc);
/*
* wait for reply handlers to drop their request refs and
* their inode/dcache refs
*/
ceph_msgr_flush();
}
/*