[PATCH (resend)] xfs: don't allow recursion into fs under write_begin

Eric Sandeen
2010-05-22T16:23:03Z

Michael Monnerie reported this fantastic stack overflow:

[21877.948005] BUG: scheduling while atomic: rsync/2345/0xffff8800
[21877.948005] Modules linked in: af_packet nfs lockd fscache nfs_acl auth_rpcgss sunrpc ipv6 ramzswap xvmalloc lzo_decompress lzo_compress loop dm_mod reiserfs xfs exportfs xennet xenblk cdrom
[21877.948005] Pid: 2345, comm: rsync Not tainted 2.6.31.12-0.2-xen #1
[21877.948005] Call Trace:
[21877.949649] [<ffffffff800119b9>] try_stack_unwind+0x189/0x1b0
[21877.949659] [<ffffffff8000f466>] dump_trace+0xa6/0x1e0
[21877.949666] [<ffffffff800114c4>] show_trace_log_lvl+0x64/0x90
[21877.949676] [<ffffffff80011513>] show_trace+0x23/0x40
[21877.949684] [<ffffffff8046b92c>] dump_stack+0x81/0x9e
[21877.949695] [<ffffffff8003f398>] __schedule_bug+0x78/0x90
[21877.949702] [<ffffffff8046c97c>] thread_return+0x1d7/0x3fb
[21877.949709] [<ffffffff8046cf85>] schedule_timeout+0x195/0x200
[21877.949717] [<ffffffff8046be2b>] wait_for_common+0x10b/0x230
[21877.949726] [<ffffffff8046c09b>] wait_for_completion+0x2b/0x50
[21877.949768] [<ffffffffa009e741>] xfs_buf_iowait+0x31/0x80 [xfs]
[21877.949894] [<ffffffffa009ea30>] _xfs_buf_read+0x70/0x80 [xfs]
[21877.949992] [<ffffffffa009ef8b>] xfs_buf_read_flags+0x8b/0xd0 [xfs]
[21877.950089] [<ffffffffa0091ab9>] xfs_trans_read_buf+0x1e9/0x320 [xfs]
[21877.950174] [<ffffffffa005b278>] xfs_btree_read_buf_block+0x68/0xe0 [xfs]
[21877.950232] [<ffffffffa005b99e>] xfs_btree_lookup_get_block+0x8e/0x110 [xfs]
[21877.950281] [<ffffffffa005c0af>] xfs_btree_lookup+0xdf/0x4d0 [xfs]
[21877.950329] [<ffffffffa0042b77>] xfs_alloc_lookup_eq+0x27/0x50 [xfs]
[21877.950361] [<ffffffffa0042f09>] xfs_alloc_fixup_trees+0x249/0x370 [xfs]
[21877.950397] [<ffffffffa0044c30>] xfs_alloc_ag_vextent_near+0x4e0/0x9a0 [xfs]
[21877.950432] [<ffffffffa00451f5>] xfs_alloc_ag_vextent+0x105/0x160 [xfs]
[21877.950471] [<ffffffffa0045bb4>] xfs_alloc_vextent+0x3b4/0x4b0 [xfs]
[21877.950504] [<ffffffffa0058da8>] xfs_bmbt_alloc_block+0xf8/0x210 [xfs]
[21877.950550] [<ffffffffa005e3b7>] xfs_btree_split+0xc7/0x720 [xfs]
[21877.950597] [<ffffffffa005ef8c>] xfs_btree_make_block_unfull+0x15c/0x1c0 [xfs]
[21877.950643] [<ffffffffa005f3ff>] xfs_btree_insrec+0x40f/0x5c0 [xfs]
[21877.950689] [<ffffffffa005f651>] xfs_btree_insert+0xa1/0x1b0 [xfs]
[21877.950748] [<ffffffffa005325e>] xfs_bmap_add_extent_delay_real+0x82e/0x12a0 [xfs]
[21877.950787] [<ffffffffa00540f4>] xfs_bmap_add_extent+0x424/0x450 [xfs]
[21877.950833] [<ffffffffa00573f3>] xfs_bmapi+0xda3/0x1320 [xfs]
[21877.950879] [<ffffffffa007c248>] xfs_iomap_write_allocate+0x1d8/0x3f0 [xfs]
[21877.950953] [<ffffffffa007d089>] xfs_iomap+0x2c9/0x300 [xfs]
[21877.951021] [<ffffffffa009a1b8>] xfs_map_blocks+0x38/0x60 [xfs]
[21877.951108] [<ffffffffa009b93a>] xfs_page_state_convert+0x3fa/0x720 [xfs]
[21877.951204] [<ffffffffa009bde4>] xfs_vm_writepage+0x84/0x160 [xfs]
[21877.951301] [<ffffffff800e3603>] pageout+0x143/0x2b0
[21877.951308] [<ffffffff800e514e>] shrink_page_list+0x26e/0x650
[21877.951314] [<ffffffff800e5803>] shrink_inactive_list+0x2d3/0x7c0
[21877.951320] [<ffffffff800e5d4b>] shrink_list+0x5b/0x110
[21877.951325] [<ffffffff800e5f71>] shrink_zone+0x171/0x250
[21877.951330] [<ffffffff800e60d3>] shrink_zones+0x83/0x120
[21877.951336] [<ffffffff800e620e>] do_try_to_free_pages+0x9e/0x380
[21877.951342] [<ffffffff800e6607>] try_to_free_pages+0x77/0xa0
[21877.951349] [<ffffffff800dbfa3>] __alloc_pages_slowpath+0x2d3/0x5c0
[21877.951355] [<ffffffff800dc3e1>] __alloc_pages_nodemask+0x151/0x160
[21877.951362] [<ffffffff800d44b7>] __page_cache_alloc+0x27/0x50
[21877.951368] [<ffffffff800d68ca>] grab_cache_page_write_begin+0x9a/0xe0
[21877.951376] [<ffffffff8014bdfe>] block_write_begin+0xae/0x120
[21877.951396] [<ffffffffa009ac24>] xfs_vm_write_begin+0x34/0x50 [xfs]
[21877.951482] [<ffffffff800d4b31>] generic_perform_write+0xc1/0x1f0
[21877.951489] [<ffffffff800d5d00>] generic_file_buffered_write+0x90/0x160
[21877.951512] [<ffffffffa00a4711>] xfs_write+0x521/0xb60 [xfs]
[21877.951624] [<ffffffffa009fb80>] xfs_file_aio_write+0x70/0xa0 [xfs]
[21877.951711] [<ffffffff80118c42>] do_sync_write+0x102/0x160
[21877.951718] [<ffffffff80118fc8>] vfs_write+0xd8/0x1c0
[21877.951723] [<ffffffff8011995b>] sys_write+0x5b/0xa0
[21877.951729] [<ffffffff8000c868>] system_call_fastpath+0x16/0x1b
[21877.951736] [<00007fc41b0fab10>] 0x7fc41b0fab10
[21877.951750] BUG: unable to handle kernel paging request at 0000000108743280
[21877.951755] IP: [<ffffffff80034832>] dequeue_task+0x72/0x110
[21877.951766] PGD 31c6f067 PUD 0
[21877.951770] Thread overran stack, or stack corrupted

I don't think we can afford to let write_begin recurse into the fs,
so we can set AOP_FLAG_NOFS ... is this too big a hammer?

Reported-by: Michael Monnerie <michael.monnerie@is.it-management.at>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---

(resend with linux-fsdevel and linux-mm per Christoph's request)

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 57c3827..3fb2cc8 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -1678,6 +1678,8 @@ xfs_vm_write_begin(
void **fsdata)
{
*pagep = NULL;
+ /* can't afford to recurse into fs due to stack reasons */
+ flags |= AOP_FLAG_NOFS;
return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
xfs_get_blocks);
}

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