XFS memory allocation deadlock in 2.6.38

[Sean Noonan]

> Can you check if the brute force patch below helps?  

Not sure if this helps at all, but here is the stack from all three processes involved.  This is without MAP_POPULATE and with the patch you just sent.

# ps aux | grep 'D[+]*[[:space:]]'
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      2314  0.2  0.0      0     0 ?        D    19:44   0:00 [flush-8:0]
root      2402  0.0  0.0      0     0 ?        D    19:44   0:00 [xfssyncd/sda9]
root      3861  2.6  9.9 16785280 4912848 pts/0 D+  19:45   0:07 ./vmtest /xfs/hugefile.dat 17179869184

# for p in 2314 2402 3861; do echo $p; cat /proc/$p/stack; done
2314
[<ffffffff810d634a>] congestion_wait+0x7a/0x130
[<ffffffff8129721c>] kmem_alloc+0x6c/0xf0
[<ffffffff8127c07e>] xfs_inode_item_format+0x36e/0x3b0
[<ffffffff8128401f>] xfs_log_commit_cil+0x4f/0x3b0
[<ffffffff8128ff31>] _xfs_trans_commit+0x1f1/0x2b0
[<ffffffff8127c716>] xfs_iomap_write_allocate+0x1a6/0x340
[<ffffffff81298883>] xfs_map_blocks+0x193/0x2c0
[<ffffffff812992fa>] xfs_vm_writepage+0x1ca/0x520
[<ffffffff810c4bd2>] __writepage+0x12/0x40
[<ffffffff810c53dd>] write_cache_pages+0x1dd/0x4f0
[<ffffffff810c573c>] generic_writepages+0x4c/0x70
[<ffffffff812986b8>] xfs_vm_writepages+0x58/0x70
[<ffffffff810c577c>] do_writepages+0x1c/0x40
[<ffffffff811247d1>] writeback_single_inode+0xf1/0x240
[<ffffffff81124edd>] writeback_sb_inodes+0xdd/0x1b0
[<ffffffff81125966>] writeback_inodes_wb+0x76/0x160
[<ffffffff81125d93>] wb_writeback+0x343/0x550
[<ffffffff81126126>] wb_do_writeback+0x186/0x2e0
[<ffffffff81126342>] bdi_writeback_thread+0xc2/0x310
[<ffffffff81067846>] kthread+0x96/0xa0
[<ffffffff8165a414>] kernel_thread_helper+0x4/0x10
[<ffffffffffffffff>] 0xffffffffffffffff
2402
[<ffffffff8106d0ec>] down+0x3c/0x50
[<ffffffff8129a7bd>] xfs_buf_lock+0x5d/0x170
[<ffffffff8128a87d>] xfs_getsb+0x1d/0x50
[<ffffffff81291bcf>] xfs_trans_getsb+0x5f/0x150
[<ffffffff8128b80e>] xfs_mod_sb+0x4e/0xe0
[<ffffffff81271dbf>] xfs_fs_log_dummy+0x4f/0x90
[<ffffffff812a61c1>] xfs_sync_worker+0x81/0x90
[<ffffffff812a6092>] xfssyncd+0x172/0x220
[<ffffffff81067846>] kthread+0x96/0xa0
[<ffffffff8165a414>] kernel_thread_helper+0x4/0x10
[<ffffffffffffffff>] 0xffffffffffffffff
3861
[<ffffffff812ec744>] call_rwsem_down_read_failed+0x14/0x30
[<ffffffff812754dd>] xfs_ilock+0x9d/0x110
[<ffffffff8127556e>] xfs_ilock_map_shared+0x1e/0x50
[<ffffffff81297c45>] __xfs_get_blocks+0xc5/0x4e0
[<ffffffff8129808c>] xfs_get_blocks+0xc/0x10
[<ffffffff81135ca2>] do_mpage_readpage+0x462/0x660
[<ffffffff81135eea>] mpage_readpage+0x4a/0x60
[<ffffffff812986e3>] xfs_vm_readpage+0x13/0x20
[<ffffffff810bd150>] filemap_fault+0x2d0/0x4e0
[<ffffffff810db0a0>] __do_fault+0x50/0x4f0
[<ffffffff810db85e>] handle_pte_fault+0x7e/0xc90
[<ffffffff810ddbf8>] handle_mm_fault+0x138/0x230
[<ffffffff8102b37c>] do_page_fault+0x12c/0x420
[<ffffffff81658fcf>] page_fault+0x1f/0x30
[<ffffffffffffffff>] 0xffffffffffffffff