jbd2: Remove __GFP_NOFAIL from jbd2 layer

__GFP_NOFAIL is going away, so add our own retry loop.  Also add
jbd2__journal_start() and jbd2__journal_restart() which take a gfp
mask, so that file systems can optionally (re)start transaction
handles using GFP_KERNEL.  If they do this, then they need to be
prepared to handle receiving an PTR_ERR(-ENOMEM) error, and be ready
to reflect that error up to userspace.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 12 insertions, 3 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index f7bf15787d68..a79d3345b55a 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -41,6 +41,7 @@
 #include <linux/hash.h>
 #include <linux/log2.h>
 #include <linux/vmalloc.h>
+#include <linux/backing-dev.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/jbd2.h>
@@ -48,8 +49,6 @@
 #include <asm/uaccess.h>
 #include <asm/page.h>
 
-EXPORT_SYMBOL(jbd2_journal_start);
-EXPORT_SYMBOL(jbd2_journal_restart);
 EXPORT_SYMBOL(jbd2_journal_extend);
 EXPORT_SYMBOL(jbd2_journal_stop);
 EXPORT_SYMBOL(jbd2_journal_lock_updates);
@@ -311,7 +310,17 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
          */
         J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
 
-        new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
+retry_alloc:
+        new_bh = alloc_buffer_head(GFP_NOFS);
+        if (!new_bh) {
+                /*
+                 * Failure is not an option, but __GFP_NOFAIL is going
+                 * away; so we retry ourselves here.
+                 */
+                congestion_wait(BLK_RW_ASYNC, HZ/50);
+                goto retry_alloc;
+        }
+
         /* keep subsequent assertions sane */
         new_bh->b_state = 0;
         init_buffer(new_bh, NULL, NULL);