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jbd2: revert must-not-fail allocation loops back to GFP_NOFAIL

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This basically reverts 47def82672 (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 <mhocko@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: David Rientjes <rientjes@google.com>
This commit is contained in:
Michal Hocko 2015-06-08 10:53:10 -04:00 committed by Theodore Ts'o
parent 3dbb5eb9a3
commit 6ccaf3e2f3
2 changed files with 8 additions and 23 deletions
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11
fs/jbd2/journal.c
View File

@ -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);

20
fs/jbd2/transaction.c
View File

@ -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);