Commit bc23f0c8 authored Nov 24, 2015 by Jan Kara Committed by Theodore Ts'o Nov 24, 2015

jbd2: Fix unreclaimed pages after truncate in data=journal mode



Ted and Namjae have reported that truncated pages don't get timely
reclaimed after being truncated in data=journal mode. The following test
triggers the issue easily:

for (i = 0; i < 1000; i++) {
	pwrite(fd, buf, 1024*1024, 0);
	fsync(fd);
	fsync(fd);
	ftruncate(fd, 0);
}

The reason is that journal_unmap_buffer() finds that truncated buffers
are not journalled (jh->b_transaction == NULL), they are part of
checkpoint list of a transaction (jh->b_cp_transaction != NULL) and have
been already written out (!buffer_dirty(bh)). We clean such buffers but
we leave them in the checkpoint list. Since checkpoint transaction holds
a reference to the journal head, these buffers cannot be released until
the checkpoint transaction is cleaned up. And at that point we don't
call release_buffer_page() anymore so pages detached from mapping are
lingering in the system waiting for reclaim to find them and free them.

Fix the problem by removing buffers from transaction checkpoint lists
when journal_unmap_buffer() finds out they don't have to be there
anymore.

Reported-and-tested-by: Namjae Jeon <namjae.jeon@samsung.com>
Fixes: de1b7941
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

parent a4dad1ae

fs/jbd2/transaction.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2152,6 +2152,7 @@ static int journal_unmap_buffer(journal_t journal, struct buffer_head bh,

		if (!buffer_dirty(bh)) {
		/* bdflush has written it. We can drop it now */
		__jbd2_journal_remove_checkpoint(jh);
		goto zap_buffer;
		}

		@@ -2181,6 +2182,7 @@ static int journal_unmap_buffer(journal_t journal, struct buffer_head bh,
		/* The orphan record's transaction has
		* committed. We can cleanse this buffer */
		clear_buffer_jbddirty(bh);
		__jbd2_journal_remove_checkpoint(jh);
		goto zap_buffer;
		}
		}

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