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authorSteven Whitehouse <swhiteho@redhat.com>2010-11-03 20:01:07 +0000
committerSteven Whitehouse <swhiteho@redhat.com>2010-11-15 12:44:42 +0000
commit044b9414c7caf9a26192c73a5b88fa1a8a32a1c1 (patch)
tree9596bb669a68b04eebc40864c3b3fd71d3d1e273 /fs/gfs2/aops.c
parent0143832cc96d0bf78486297aad5c8fb2c2ead02a (diff)
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GFS2: Fix inode deallocation race
This area of the code has always been a bit delicate due to the subtleties of lock ordering. The problem is that for "normal" alloc/dealloc, we always grab the inode locks first and the rgrp lock later. In order to ensure no races in looking up the unlinked, but still allocated inodes, we need to hold the rgrp lock when we do the lookup, which means that we can't take the inode glock. The solution is to borrow the technique already used by NFS to solve what is essentially the same problem (given an inode number, look up the inode carefully, checking that it really is in the expected state). We cannot do that directly from the allocation code (lock ordering again) so we give the job to the pre-existing delete workqueue and carry on with the allocation as normal. If we find there is no space, we do a journal flush (required anyway if space from a deallocation is to be released) which should block against the pending deallocations, so we should always get the space back. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/aops.c')
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