Jeff Moyer <jmoyer <at> redhat.com> writes: > > Hi, Linus, > > Jens is still on vacation, and this is a pretty important patch to get > merged. Would you mind taking a look? > > This commit: > > commit 080399aaaf3531f5b8761ec0ac30ff98891e8686 > Author: Jeff Moyer <jmoyer <at> redhat.com> > Date: Fri May 11 16:34:10 2012 +0200 > > 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. > > 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. > > Comments, as always, are appreciated. > > Signed-off-by: Jeff Moyer <jmoyer <at> redhat.com> > Reported-and-Tested-by: Torsten Hilbrich <torsten.hilbrich <at> secunet.com> > Tested-by: Richard W.M. Jones <rjones <at> redhat.com> > Cc: Stable <stable <at> vger.kernel.org>
For what it's worth, we've been carrying this patch in Fedora for a couple of weeks now. It has been confirmed to fix: https://bugzilla.redhat.com/show_bug.cgi?id=835019 Feel free to include a: Reviewed-by: Josh Boyer <jwbo...@redhat.com> if you'd like. josh > > -- > Stable Notes: this patch requires backport to 3.0, 3.2 and 3.3. > > diff --git a/fs/buffer.c b/fs/buffer.c > index 838a9cf..c7062c8 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1036,6 +1036,9 @@ grow_buffers(struct block_device *bdev, sector_t block, > int size) > static struct buffer_head * > __getblk_slow(struct block_device *bdev, sector_t block, int size) > { > + int ret; > + struct buffer_head *bh; > + > /* Size must be multiple of hard sectorsize */ > if (unlikely(size & (bdev_logical_block_size(bdev)-1) || > (size < 512 || size > PAGE_SIZE))) { > @@ -1048,20 +1051,21 @@ __getblk_slow(struct block_device *bdev, sector_t > block, int size) > return NULL; > } > > - for (;;) { > - struct buffer_head * bh; > - int ret; > +retry: > + bh = __find_get_block(bdev, block, size); > + if (bh) > + return bh; > > + ret = grow_buffers(bdev, block, size); > + if (ret == 0) { > + free_more_memory(); > + goto retry; > + } else if (ret > 0) { > 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(); > } > + return NULL; > } > > /* > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
