Commit 6ccaf3e2 authored by Michal Hocko's avatar Michal Hocko Committed by Theodore Ts'o
Browse files

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



This basically reverts 47def826 (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: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
parent 3dbb5eb9

fs/jbd2/journal.c

+1 −10
Original line number Diff line number Diff line
@@ -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);

fs/jbd2/transaction.c

+7 −13
Original line number Diff line number Diff line
@@ -278,23 +278,17 @@ static int start_this_handle(journal_t *journal, handle_t *handle, 


alloc_transaction:

	if (!journal->j_running_transaction) {

		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_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) {

				congestion_wait(BLK_RW_ASYNC, HZ/50);

				goto alloc_transaction;

			}

		if ((gfp_mask & __GFP_FS) == 0)

			gfp_mask |= __GFP_NOFAIL;

		new_transaction = kmem_cache_zalloc(transaction_cache,

						    gfp_mask);

		if (!new_transaction)

			return -ENOMEM;

	}

	}



	jbd_debug(3, "New handle %p going live.\n", handle);

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