On Tue 18-08-15 12:40:31, Michal Hocko wrote:
[...]
> @@ -4867,9 +4865,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
> return NULL;
>
> for (i = 0; i < num_pages; i++, index++) {
> - p = find_or_create_page(mapping, index, GFP_NOFS);
> - if (!p)
> - goto free_eb;
> + p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
>
> spin_lock(&mapping->private_lock);
> if (PagePrivate(p)) {
Same here. find_or_create_page might return NULL.
---
>From f430e5f54367b8815e1099f26fedd2873b597a07 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Wed, 15 Jul 2015 19:27:06 +0200
Subject: [PATCH] btrfs: Prevent from early transaction abort
Btrfs relies on GFP_NOFS allocation when commiting the transaction but
since "mm: page_alloc: do not lock up GFP_NOFS allocations upon OOM"
those allocations are allowed to fail which can lead to a pre-mature
transaction abort:
[ 55.328093] Call Trace:
[ 55.328890] [<ffffffff8154e6f0>] dump_stack+0x4f/0x7b
[ 55.330518] [<ffffffff8108fa28>] ? console_unlock+0x334/0x363
[ 55.332738] [<ffffffff8110873e>] __alloc_pages_nodemask+0x81d/0x8d4
[ 55.334910] [<ffffffff81100752>] pagecache_get_page+0x10e/0x20c
[ 55.336844] [<ffffffffa007d916>] alloc_extent_buffer+0xd0/0x350 [btrfs]
[ 55.338973] [<ffffffffa0059d8c>] btrfs_find_create_tree_block+0x15/0x17 [btrfs]
[ 55.341329] [<ffffffffa004f728>] btrfs_alloc_tree_block+0x18c/0x405 [btrfs]
[ 55.343566] [<ffffffffa003fa34>] split_leaf+0x1e4/0x6a6 [btrfs]
[ 55.345577] [<ffffffffa0040567>] btrfs_search_slot+0x671/0x831 [btrfs]
[ 55.347679] [<ffffffff810682d7>] ? get_parent_ip+0xe/0x3e
[ 55.349434] [<ffffffffa0041cb2>] btrfs_insert_empty_items+0x5d/0xa8 [btrfs]
[ 55.351681] [<ffffffffa004ecfb>] __btrfs_run_delayed_refs+0x7a6/0xf35 [btrfs]
[ 55.353979] [<ffffffffa00512ea>] btrfs_run_delayed_refs+0x6e/0x226 [btrfs]
[ 55.356212] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.358378] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.360626] [<ffffffffa0060221>] btrfs_commit_transaction+0x4c/0xaba [btrfs]
[ 55.362894] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.365221] [<ffffffffa0073428>] btrfs_sync_file+0x29c/0x310 [btrfs]
[ 55.367273] [<ffffffff81186808>] vfs_fsync_range+0x8f/0x9e
[ 55.369047] [<ffffffff81186833>] vfs_fsync+0x1c/0x1e
[ 55.370654] [<ffffffff81186869>] do_fsync+0x34/0x4e
[ 55.372246] [<ffffffff81186ab3>] SyS_fsync+0x10/0x14
[ 55.373851] [<ffffffff81554f97>] system_call_fastpath+0x12/0x6f
[ 55.381070] BTRFS: error (device hdb1) in btrfs_run_delayed_refs:2821: errno=-12 Out of memory
[ 55.382431] BTRFS warning (device hdb1): Skipping commit of aborted transaction.
[ 55.382433] BTRFS warning (device hdb1): cleanup_transaction:1692: Aborting unused transaction(IO failure).
[ 55.384280] ------------[ cut here ]------------
[ 55.384312] WARNING: CPU: 0 PID: 3010 at fs/btrfs/delayed-ref.c:438 btrfs_select_ref_head+0xd9/0xfe [btrfs]()
[...]
[ 55.384337] Call Trace:
[ 55.384353] [<ffffffff8154e6f0>] dump_stack+0x4f/0x7b
[ 55.384357] [<ffffffff8107f717>] ? down_trylock+0x2d/0x37
[ 55.384359] [<ffffffff81046977>] warn_slowpath_common+0xa1/0xbb
[ 55.384398] [<ffffffffa00a1d6b>] ? btrfs_select_ref_head+0xd9/0xfe [btrfs]
[ 55.384400] [<ffffffff81046a34>] warn_slowpath_null+0x1a/0x1c
[ 55.384423] [<ffffffffa00a1d6b>] btrfs_select_ref_head+0xd9/0xfe [btrfs]
[ 55.384446] [<ffffffffa004e5f7>] ? __btrfs_run_delayed_refs+0xa2/0xf35 [btrfs]
[ 55.384455] [<ffffffffa004e600>] __btrfs_run_delayed_refs+0xab/0xf35 [btrfs]
[ 55.384476] [<ffffffffa00512ea>] btrfs_run_delayed_refs+0x6e/0x226 [btrfs]
[ 55.384499] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.384521] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.384543] [<ffffffffa0060221>] btrfs_commit_transaction+0x4c/0xaba [btrfs]
[ 55.384565] [<ffffffffa0060e21>] ? start_transaction+0x192/0x534 [btrfs]
[ 55.384588] [<ffffffffa0073428>] btrfs_sync_file+0x29c/0x310 [btrfs]
[ 55.384591] [<ffffffff81186808>] vfs_fsync_range+0x8f/0x9e
[ 55.384592] [<ffffffff81186833>] vfs_fsync+0x1c/0x1e
[ 55.384593] [<ffffffff81186869>] do_fsync+0x34/0x4e
[ 55.384594] [<ffffffff81186ab3>] SyS_fsync+0x10/0x14
[ 55.384595] [<ffffffff81554f97>] system_call_fastpath+0x12/0x6f
[...]
[ 55.384608] ---[ end trace c29799da1d4dd621 ]---
[ 55.437323] BTRFS info (device hdb1): forced readonly
[ 55.438815] BTRFS info (device hdb1): delayed_refs has NO entry
Fix this by reintroducing the no-fail behavior of this allocation path
with the explicit __GFP_NOFAIL.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
fs/btrfs/extent_io.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c374e1e71e5f..f4d6eea975d7 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4607,9 +4607,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
{
struct extent_buffer *eb = NULL;
- eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS);
- if (eb == NULL)
- return NULL;
+ eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
eb->start = start;
eb->len = len;
eb->fs_info = fs_info;
@@ -4867,7 +4865,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
return NULL;
for (i = 0; i < num_pages; i++, index++) {
- p = find_or_create_page(mapping, index, GFP_NOFS);
+ p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
if (!p)
goto free_eb;
--
2.5.0
--
Michal Hocko
SUSE Labs
--
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