Darrick J. Wong 6d43e485e0 xfs: clear _XBF_PAGES from buffers when readahead page
commit 2aa6ba7b5ad3189cc27f14540aa2f57f0ed8df4b upstream.

If we try to allocate memory pages to back an xfs_buf that we're trying
to read, it's possible that we'll be so short on memory that the page
allocation fails.  For a blocking read we'll just wait, but for
readahead we simply dump all the pages we've collected so far.

Unfortunately, after dumping the pages we neglect to clear the
_XBF_PAGES state, which means that the subsequent call to xfs_buf_free
thinks that b_pages still points to pages we own.  It then double-frees
the b_pages pages.

This results in screaming about negative page refcounts from the memory
manager, which xfs oughtn't be triggering.  To reproduce this case,
mount a filesystem where the size of the inodes far outweighs the
availalble memory (a ~500M inode filesystem on a VM with 300MB memory
did the trick here) and run bulkstat in parallel with other memory
eating processes to put a huge load on the system.  The "check summary"
phase of xfs_scrub also works for this purpose.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Cc: Ivan Kozik <ivan@ludios.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-03-30 09:35:19 +02:00
..
2015-06-30 19:44:57 -07:00
2017-02-09 08:02:45 +01:00
2015-06-25 17:00:42 -07:00
2017-03-12 06:37:28 +01:00
2016-11-10 16:36:34 +01:00
2015-11-13 20:34:33 -05:00
2015-11-23 21:11:08 -05:00
2016-10-07 15:23:47 +02:00
2015-11-10 12:07:22 -08:00
2015-11-16 23:54:45 -08:00
2015-11-16 23:54:45 -08:00
2015-08-12 15:28:45 -05:00
2016-08-10 11:49:27 +02:00
2016-05-18 17:06:48 -07:00
2016-09-07 08:32:43 +02:00
2015-11-13 20:34:33 -05:00