We recently fixed an out-of-space deadlock in XFS, and part of that fix
involved the addition of the XFS_ALLOC_FLAG_FREEING flag to some of the
space allocator calls to indicate they're freeing space, not allocating
it. There was a missed xfs_alloc_fix_freelist condition test that did not
correctly test "flags". The same test would also test an uninitialised
structure field (args->userdata) and depending on its value either would
or would not return early with a critical buffer pointer set to NULL.

This fixes that up, adds asserts to several places to catch future botches
of this nature, and skips sections of xfs_alloc_fix_freelist that are
irrelevent for the space-freeing case.

SGI-PV: 955303
SGI-Modid: xfs-linux-melb:xfs-kern:26743a
Signed-off-by: NNathan Scott <nathans@sgi.com>

pure bloat.

SGI-PV: 952969
SGI-Modid: xfs-linux-melb:xfs-kern:26251a
Signed-off-by: NNathan Scott <nathans@sgi.com>

transaction within each such operation may involve multiple locking of AGF
buffer. While the freeing extent function has sorted the extents based on
AGF number before entering into transaction, however, when the file system
space is very limited, the allocation of space would try every AGF to get
space allocated, this could potentially cause out-of-order locking, thus
deadlock could happen. This fix mitigates the scarce space for allocation
by setting aside a few blocks without reservation, and avoid deadlock by
maintaining ascending order of AGF locking.

SGI-PV: 947395
SGI-Modid: xfs-linux-melb:xfs-kern:210801a
Signed-off-by: NYingping Lu <yingping@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>

AG freelist.

SGI-PV: 952681
SGI-Modid: xfs-linux-melb:xfs-kern:25902a
Signed-off-by: NNathan Scott <nathans@sgi.com>

these typos.

SGI-PV: 904196
SGI-Modid: xfs-linux-melb:xfs-kern:25539a
Signed-off-by: NNathan Scott <nathans@sgi.com>

SGI-PV: 943272
SGI-Modid: xfs-linux:xfs-kern:201006a
Signed-off-by: NChristoph Hellwig <hch@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>

boilerplate.

SGI-PV: 913862
SGI-Modid: xfs-linux:xfs-kern:23903a
Signed-off-by: NNathan Scott <nathans@sgi.com>

SGI-PV: 943122
SGI-Modid: xfs-linux:xfs-kern:23901a
Signed-off-by: NNathan Scott <nathans@sgi.com>

SGI-PV: 936255
SGI-Modid: xfs-linux:xfs-kern:192760a
Signed-off-by: NChristoph Hellwig <hch@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!