From: Michal Hocko <mho...@suse.com>

Journal transaction might fail prematurely because the frozen_buffer
is allocated by GFP_NOFS request:
[   72.440013] do_get_write_access: OOM for frozen_buffer
[   72.440014] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: 
Out of memory in __ext4_journal_get_write_access
[   72.440015] EXT4-fs error (device sda1) in ext4_reserve_inode_write:4735: 
Out of memory
(...snipped....)
[   72.495559] do_get_write_access: OOM for frozen_buffer
[   72.495560] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: 
Out of memory in __ext4_journal_get_write_access
[   72.496839] do_get_write_access: OOM for frozen_buffer
[   72.496841] EXT4-fs: ext4_reserve_inode_write:4729: aborting transaction: 
Out of memory in __ext4_journal_get_write_access
[   72.505766] Aborting journal on device sda1-8.
[   72.505851] EXT4-fs (sda1): Remounting filesystem read-only

This wasn't a problem until "mm: page_alloc: do not lock up GFP_NOFS
allocations upon OOM" because small GPF_NOFS allocations never failed.
This allocation seems essential for the journal and GFP_NOFS is too
restrictive to the memory allocator so let's use __GFP_NOFAIL here to
emulate the previous behavior.

jbd code has the very same issue so let's do the same there as well.

Signed-off-by: Michal Hocko <mho...@suse.com>
---
 fs/jbd/transaction.c  | 11 +----------
 fs/jbd2/transaction.c | 14 +++-----------
 2 files changed, 4 insertions(+), 21 deletions(-)

diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 1695ba8334a2..bf7474deda2f 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -673,16 +673,7 @@ do_get_write_access(handle_t *handle, struct journal_head 
*jh,
                                jbd_unlock_bh_state(bh);
                                frozen_buffer =
                                        jbd_alloc(jh2bh(jh)->b_size,
-                                                        GFP_NOFS);
-                               if (!frozen_buffer) {
-                                       printk(KERN_ERR
-                                              "%s: OOM for frozen_buffer\n",
-                                              __func__);
-                                       JBUFFER_TRACE(jh, "oom!");
-                                       error = -ENOMEM;
-                                       jbd_lock_bh_state(bh);
-                                       goto done;
-                               }
+                                                        GFP_NOFS|__GFP_NOFAIL);
                                goto repeat;
                        }
                        jh->b_frozen_data = frozen_buffer;
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index ff2f2e6ad311..bff071e21553 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -923,16 +923,7 @@ do_get_write_access(handle_t *handle, struct journal_head 
*jh,
                                jbd_unlock_bh_state(bh);
                                frozen_buffer =
                                        jbd2_alloc(jh2bh(jh)->b_size,
-                                                        GFP_NOFS);
-                               if (!frozen_buffer) {
-                                       printk(KERN_ERR
-                                              "%s: OOM for frozen_buffer\n",
-                                              __func__);
-                                       JBUFFER_TRACE(jh, "oom!");
-                                       error = -ENOMEM;
-                                       jbd_lock_bh_state(bh);
-                                       goto done;
-                               }
+                                                        GFP_NOFS|__GFP_NOFAIL);
                                goto repeat;
                        }
                        jh->b_frozen_data = frozen_buffer;
@@ -1157,7 +1148,8 @@ int jbd2_journal_get_undo_access(handle_t *handle, struct 
buffer_head *bh)
 
 repeat:
        if (!jh->b_committed_data) {
-               committed_data = jbd2_alloc(jh2bh(jh)->b_size, GFP_NOFS);
+               committed_data = jbd2_alloc(jh2bh(jh)->b_size,
+                                           GFP_NOFS|__GFP_NOFAIL);
                if (!committed_data) {
                        printk(KERN_ERR "%s: No memory for committed data\n",
                                __func__);
-- 
2.5.0

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