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  1. 20 Jun, 2014 4 commits
    • Vlastimil Babka's avatar
      mm: compaction: detect when scanners meet in isolate_freepages · 31662557
      Vlastimil Babka authored 
      commit 7ed695e0 upstream.

Compaction of a zone is finished when the migrate scanner (which begins
at the zone's lowest pfn) meets the free page scanner (which begins at
the zone's highest pfn).  This is detected in compact_zone() and in the
case of direct compaction, the compact_blockskip_flush flag is set so
that kswapd later resets the cached scanner pfn's, and a new compaction
may again start at the zone's borders.

The meeting of the scanners can happen during either scanner's activity.
However, it may currently fail to be detected when it occurs in the free
page scanner, due to two problems.  First, isolate_freepages() keeps
free_pfn at the highest block where it isolated pages from, for the
purposes of not missing the pages that are returned back to allocator
when migration fails.  Second, failing to isolate enough free pages due
to scanners meeting results in -ENOMEM being returned by
migrate_pages(), which makes compact_zone() bail out immediately without
calling compact_finished() that would detect scanners meeting.

This failure to detect scanners meeting might result in repeated
attempts at compaction of a zone that keep starting from the cached
pfn's close to the meeting point, and quickly failing through the
-ENOMEM path, without the cached pfns being reset, over and over.  This
has been observed (through additional tracepoints) in the third phase of
the mmtests stress-highalloc benchmark, where the allocator runs on an
otherwise idle system.  The problem was observed in the DMA32 zone,
which was used as a fallback to the preferred Normal zone, but on the
4GB system it was actually the largest zone.  The problem is even
amplified for such fallback zone - the deferred compaction logic, which
could (after being fixed by a previous patch) reset the cached scanner
pfn's, is only applied to the preferred zone and not for the fallbacks.

The problem in the third phase of the benchmark was further amplified by
commit 81c0a2bb ("mm: page_alloc: fair zone allocator policy") which
resulted in a non-deterministic regression of the allocation success
rate from ~85% to ~65%.  This occurs in about half of benchmark runs,
making bisection problematic.  It is unlikely that the commit itself is
buggy, but it should put more pressure on the DMA32 zone during phases 1
and 2, which may leave it more fragmented in phase 3 and expose the bugs
that this patch fixes.

The fix is to make scanners meeting in isolate_freepage() stay that way,
and to check in compact_zone() for scanners meeting when migrate_pages()
returns -ENOMEM.  The result is that compact_finished() also detects
scanners meeting and sets the compact_blockskip_flush flag to make
kswapd reset the scanner pfn's.

The results in stress-highalloc benchmark show that the "regression" by
commit 81c0a2bb in phase 3 no longer occurs, and phase 1 and 2
allocation success rates are also significantly improved.
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      31662557
    • Vlastimil Babka's avatar
      mm: compaction: reset cached scanner pfn's before reading them · 948ec1db
      Vlastimil Babka authored 
      commit d3132e4b upstream.

Compaction caches pfn's for its migrate and free scanners to avoid
scanning the whole zone each time.  In compact_zone(), the cached values
are read to set up initial values for the scanners.  There are several
situations when these cached pfn's are reset to the first and last pfn
of the zone, respectively.  One of these situations is when a compaction
has been deferred for a zone and is now being restarted during a direct
compaction, which is also done in compact_zone().

However, compact_zone() currently reads the cached pfn's *before*
resetting them.  This means the reset doesn't affect the compaction that
performs it, and with good chance also subsequent compactions, as
update_pageblock_skip() is likely to be called and update the cached
pfn's to those being processed.  Another chance for a successful reset
is when a direct compaction detects that migration and free scanners
meet (which has its own problems addressed by another patch) and sets
update_pageblock_skip flag which kswapd uses to do the reset because it
goes to sleep.

This is clearly a bug that results in non-deterministic behavior, so
this patch moves the cached pfn reset to be performed *before* the
values are read.
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      948ec1db
    • Nicholas Bellinger's avatar
      target: Fix NULL pointer dereference for XCOPY in target_put_sess_cmd · 9c7e0735
      Nicholas Bellinger authored 
      commit 0ed6e189 upstream.

This patch fixes a NULL pointer dereference regression bug that was
introduced with:

commit 1e1110c4
Author: Mikulas Patocka <mpatocka@redhat.com>
Date:   Sat May 17 06:49:22 2014 -0400

    target: fix memory leak on XCOPY

Now that target_put_sess_cmd() -> kref_put_spinlock_irqsave() is
called with a valid se_cmd->cmd_kref, a NULL pointer dereference
is triggered because the XCOPY passthrough commands don't have
an associated se_session pointer.

To address this bug, go ahead and checking for a NULL se_sess pointer
within target_put_sess_cmd(), and call se_cmd->se_tfo->release_cmd()
to release the XCOPY's xcopy_pt_cmd memory.
Reported-by: default avatarThomas Glanzmann <thomas@glanzmann.de>
Cc: Thomas Glanzmann <thomas@glanzmann.de>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org # 3.12+
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      9c7e0735
    • Justin Maggard's avatar
      btrfs: fix defrag 32-bit integer overflow · 6e8451cb
      Justin Maggard authored 
      commit c41570c9 upstream.

When defragging a very large file, the cluster variable can wrap its 32-bit
signed int type and become negative, which eventually gets passed to
btrfs_force_ra() as a very large unsigned long value.  On 32-bit platforms,
this eventually results in an Oops from the SLAB allocator.

Change the cluster and max_cluster signed int variables to unsigned long to
match the readahead functions.  This also allows the min() comparison in
btrfs_defrag_file() to work as intended.
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      6e8451cb
  3. 18 Jun, 2014 7 commits
  5. 11 Jun, 2014 2 commits
  7. 09 Jun, 2014 27 commits
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