xfs: fix getbmap vs mmap deadlock
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 <923f7720577207a44b32e59bbfbea59d27f1ae8e@lst.de>
Reviewed-by: Eric Sandeen <d55521028c14e0f378be5444e4ea388161c0d7e7@sandeen.net>
Reviewed-by: Felix Blyakher <489795e92d328beb2187b977cd7059f2eaf90933@sgi.com>
Signed-off-by: Felix Blyakher <489795e92d328beb2187b977cd7059f2eaf90933@sgi.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs