xfs: fix getbmap vs mmap deadlock
xfs_getbmap (or rather the formatters called by it) copy out the getbmap structures under the ilock, which can deadlock against mmap. This has been reported via bugzilla a while ago (#717) and has recently also shown up via lockdep. So allocate a temporary buffer to format the kernel getbmap structures into and then copy them out after dropping the locks. A little problem with this is that we limit the number of extents we can copy out by the maximum allocation size, but I see no real way around that. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Eric Sandeen <sandeen@sandeen.net> Reviewed-by: Felix Blyakher <felixb@sgi.com> Signed-off-by: Felix Blyakher <felixb@sgi.com>
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