Messages in this thread | | | Date | Thu, 6 Feb 2014 12:03:48 -0500 | From | "J. Bruce Fields" <> | Subject | Re: [PATCH] dcache: make d_splice_alias use d_materialise_unique |
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On Fri, Jan 31, 2014 at 02:47:58PM -0500, J. Bruce Fields wrote: > (Then one remaining thing I don't understand is how to make that fixing > up reliable. Or is there some reason nobody hits the _EBUSY case of > __d_unalias?)
In fact, a reproducer found thanks to Hideshi Yamaoka:
On server:
while true; do mv /exports/DIR /exports/TO/DIR mv /exports/TO/DIR /exports/DIR done
On client:
mount -olookupcache=pos /mnt
while true; do ls /mnt/TO; done
Also on client:
while true; do strace -e open cat /mnt/DIR/test.txt 2>&1 | grep EBUSY done
Once all three of those loops are running I hit
open("/mnt/DIR/test.txt", O_RDONLY) = -1 EBUSY
very quickly.
The "lookupcache=pos" isn't really necessary but makes the reproducer more reliable.
(Originally this was seen on a single client: the client itself was doing the renames but also continually killing the second mv. I suspect that means the client sends the RENAME but then fails to update its dcache, the result being again that the client's dcache is out of sync with the server's tree and hence lookup is stuck trying to grab a dentry from another directory.)
Is there some solution short of making ->lookup callers drop the i_mutex and retry???
--b.
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