From: Jeff Moyer Subject: Re: Kernel 3.3.8 breaks accidental ext3 mount of extended partition Date: Mon, 25 Jun 2012 12:38:03 -0400 Message-ID: References: <4FDEC3C2.4060909@secunet.com> <20120625113457.GA1289@amd.home.annexia.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Torsten Hilbrich , linux-ext4@vger.kernel.org, LKML To: "Richard W.M. Jones" Return-path: In-Reply-To: <20120625113457.GA1289@amd.home.annexia.org> (Richard W. M. Jones's message of "Mon, 25 Jun 2012 12:34:57 +0100") Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org "Richard W.M. Jones" writes: > On Mon, Jun 18, 2012 at 07:59:30AM +0200, Torsten Hilbrich wrote: >> Hello, >> >> a software that tries to mount each existing partition as ext3 file system started to fail when updating from v3.3.7 to v3.3.8. >> >> The applications then hangs-up in the mount syscall, here is a snapshot of its stack at this moment: > > We just ran into what we think is the same problem. > > Note that ext4 fails like this for any 1024 byte sized filesystem (of > zeroes) that you try to mount. It's really nothing to do with > extended partitions. > > Here is a very simple reproducer + stack trace: > > https://bugzilla.redhat.com/show_bug.cgi?id=835019#c4 > > I will try out the patch suggested later on in this thread. Please try the attached patch instead. The patch I had originally posted for this allowed marking the first buffer beyond EOD as uptodate. This isn't correct. The patch I've attached below fixes the infinite loop in __getblk_slow. Cheers, Jeff 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; } /*