Patch "jbd2: Fix unreclaimed pages after truncate in data=journal mode" has been added to the 4.3-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

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

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     jbd2-fix-unreclaimed-pages-after-truncate-in-data-journal-mode.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From bc23f0c8d7ccd8d924c4e70ce311288cb3e61ea8 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 24 Nov 2015 15:34:35 -0500
Subject: jbd2: Fix unreclaimed pages after truncate in data=journal mode

From: Jan Kara <jack@suse.cz>

commit bc23f0c8d7ccd8d924c4e70ce311288cb3e61ea8 upstream.

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: de1b794130b130e77ffa975bb58cb843744f9ae5
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/jbd2/transaction.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -2152,6 +2152,7 @@ static int journal_unmap_buffer(journal_
 
 		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_
 				/* The orphan record's transaction has
 				 * committed.  We can cleanse this buffer */
 				clear_buffer_jbddirty(bh);
+				__jbd2_journal_remove_checkpoint(jh);
 				goto zap_buffer;
 			}
 		}


Patches currently in stable-queue which might be from jack@suse.cz are

queue-4.3/jbd2-fix-unreclaimed-pages-after-truncate-in-data-journal-mode.patch