summaryrefslogtreecommitdiffstats
path: root/virt
diff options
context:
space:
mode:
authorJeff Moyer <jmoyer@redhat.com>2012-07-12 15:43:14 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-13 17:36:35 +0200
commit91f68c89d8f35fe98ea04159b9a3b42d0149478f (patch)
treed62ecd2a9de58a2d5673e4e1765b35eac28faf2c /virt
parentMerge tag 'fbdev-fixes-for-3.5-2' of git://github.com/schandinat/linux-2.6 (diff)
downloadlinux-91f68c89d8f35fe98ea04159b9a3b42d0149478f.tar.xz
linux-91f68c89d8f35fe98ea04159b9a3b42d0149478f.zip
block: fix infinite loop in __getblk_slow
Commit 080399aaaf35 ("block: don't mark buffers beyond end of disk as mapped") exposed a bug in __getblk_slow that causes mount to hang as it loops infinitely waiting for a buffer that lies beyond the end of the disk to become uptodate. The problem was initially reported by Torsten Hilbrich here: https://lkml.org/lkml/2012/6/18/54 and also reported independently here: http://www.sysresccd.org/forums/viewtopic.php?f=13&t=4511 and then Richard W.M. Jones and Marcos Mello noted a few separate bugzillas also associated with the same issue. This patch has been confirmed to fix: https://bugzilla.redhat.com/show_bug.cgi?id=835019 The main problem is here, in __getblk_slow: for (;;) { struct buffer_head * bh; int ret; bh = __find_get_block(bdev, block, size); if (bh) return bh; ret = grow_buffers(bdev, block, size); if (ret < 0) return NULL; if (ret == 0) free_more_memory(); } __find_get_block does not find the block, since it will not be marked as mapped, and so grow_buffers is called to fill in the buffers for the associated page. I believe the for (;;) loop is there primarily to retry in the case of memory pressure keeping grow_buffers from succeeding. However, we also continue to loop for other cases, like the block lying beond the end of the disk. So, the fix I came up with is to only loop when grow_buffers fails due to memory allocation issues (return value of 0). The attached patch was tested by myself, Torsten, and Rich, and was found to resolve the problem in call cases. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Reported-and-Tested-by: Torsten Hilbrich <torsten.hilbrich@secunet.com> Tested-by: Richard W.M. Jones <rjones@redhat.com> Reviewed-by: Josh Boyer <jwboyer@redhat.com> Cc: Stable <stable@vger.kernel.org> # 3.0+ [ Jens is on vacation, taking this directly - Linus ] -- Stable Notes: this patch requires backport to 3.0, 3.2 and 3.3. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'virt')
0 files changed, 0 insertions, 0 deletions