ceph: fix mds sync() race with completing requests

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The wait_unsafe_requests() helper dropped the mdsc mutex to wait
for each request to complete, and then examined r_node to get the
next request after retaking the lock.  But the request completion
removes the request from the tree, so r_node was always undefined
at this point.  Since it's a small race, it usually led to a
valid request, but not always.  The result was an occasional
crash in rb_next() while dereferencing node->rb_left.

Fix this by clearing the rb_node when removing the request from
the request tree, and not walking off into the weeds when we
are done waiting for a request.  Since the request we waited on
will _always_ be out of the request tree, take a ref on the next
request, in the hopes that it won't be.  But if it is, it's ok:
we can start over from the beginning (and traverse over older read
requests again).

Signed-off-by: Sage Weil <sage@newdream.net>

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This commit is contained in:

Sage Weil 2010-03-16 15:28:54 -07:00

parent 916623da10

commit 80fc7314a7

1 changed files with 20 additions and 7 deletions

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fs/ceph/mds_client.c

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