This basically reverts 47def82672b3 (jbd2: Remove __GFP_NOFAIL from jbd2
layer). The deprecation of __GFP_NOFAIL was a bad choice because it led
to open coding the endless loop around the allocator rather than
removing the dependency on the non failing allocation. So the
deprecation was a clear failure and the reality tells us that
__GFP_NOFAIL is not even close to go away.
It is still true that __GFP_NOFAIL allocations are generally discouraged
and new uses should be evaluated and an alternative (pre-allocations or
reservations) should be considered but it doesn't make any sense to lie
the allocator about the requirements. Allocator can take steps to help
making a progress if it knows the requirements.
Signed-off-by: Michal Hocko <[email protected]>
Acked-by: David Rientjes <[email protected]>
---
Hi,
this has been posted few months ago
(http://marc.info/?l=linux-mm&m=142530454419654&w=2) but it hasn't
gone anywhere so I am reposting. I've just rebased it on top of the
ext4/for-linus tree. It wasn't clear to me which branch should I use so
I've just picked this one as it was one of the most recently updated.
fs/jbd2/journal.c | 11 +----------
fs/jbd2/transaction.c | 20 +++++++-------------
2 files changed, 8 insertions(+), 23 deletions(-)
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b96bd8076b70..0bc333b4a594 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -371,16 +371,7 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
*/
J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
-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;
- }
+ new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
/* keep subsequent assertions sane */
atomic_set(&new_bh->b_count, 1);
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index ff2f2e6ad311..799242cecffb 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -278,22 +278,16 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
alloc_transaction:
if (!journal->j_running_transaction) {
+ /*
+ * If __GFP_FS is not present, then we may be being called from
+ * inside the fs writeback layer, so we MUST NOT fail.
+ */
+ if ((gfp_mask & __GFP_FS) == 0)
+ gfp_mask |= __GFP_NOFAIL;
new_transaction = kmem_cache_zalloc(transaction_cache,
gfp_mask);
- if (!new_transaction) {
- /*
- * If __GFP_FS is not present, then we may be
- * being called from inside the fs writeback
- * layer, so we MUST NOT fail. Since
- * __GFP_NOFAIL is going away, we will arrange
- * to retry the allocation ourselves.
- */
- if ((gfp_mask & __GFP_FS) == 0) {
- congestion_wait(BLK_RW_ASYNC, HZ/50);
- goto alloc_transaction;
- }
+ if (!new_transaction)
return -ENOMEM;
- }
}
jbd_debug(3, "New handle %p going live.\n", handle);
--
2.1.4
On Mon, Jun 08, 2015 at 03:28:44PM +0200, Michal Hocko wrote:
> This basically reverts 47def82672b3 (jbd2: Remove __GFP_NOFAIL from jbd2
> layer). The deprecation of __GFP_NOFAIL was a bad choice because it led
> to open coding the endless loop around the allocator rather than
> removing the dependency on the non failing allocation. So the
> deprecation was a clear failure and the reality tells us that
> __GFP_NOFAIL is not even close to go away.
>
> It is still true that __GFP_NOFAIL allocations are generally discouraged
> and new uses should be evaluated and an alternative (pre-allocations or
> reservations) should be considered but it doesn't make any sense to lie
> the allocator about the requirements. Allocator can take steps to help
> making a progress if it knows the requirements.
>
> Signed-off-by: Michal Hocko <[email protected]>
> Acked-by: David Rientjes <[email protected]>
Applied, thanks.
- Ted
On Mon 08-06-15 10:54:32, Theodore Ts'o wrote:
> On Mon, Jun 08, 2015 at 03:28:44PM +0200, Michal Hocko wrote:
> > This basically reverts 47def82672b3 (jbd2: Remove __GFP_NOFAIL from jbd2
> > layer). The deprecation of __GFP_NOFAIL was a bad choice because it led
> > to open coding the endless loop around the allocator rather than
> > removing the dependency on the non failing allocation. So the
> > deprecation was a clear failure and the reality tells us that
> > __GFP_NOFAIL is not even close to go away.
> >
> > It is still true that __GFP_NOFAIL allocations are generally discouraged
> > and new uses should be evaluated and an alternative (pre-allocations or
> > reservations) should be considered but it doesn't make any sense to lie
> > the allocator about the requirements. Allocator can take steps to help
> > making a progress if it knows the requirements.
> >
> > Signed-off-by: Michal Hocko <[email protected]>
> > Acked-by: David Rientjes <[email protected]>
>
> Applied, thanks.
Thanks!
--
Michal Hocko
SUSE Labs