From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 820387F37 for ; Wed, 10 Jul 2013 01:28:19 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay3.corp.sgi.com (Postfix) with ESMTP id F292CAC005 for ; Tue, 9 Jul 2013 23:28:15 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com [141.146.126.69]) by cuda.sgi.com with ESMTP id JLcdO7cbreoy2D7a (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Tue, 09 Jul 2013 23:28:11 -0700 (PDT) Message-ID: <51DCFF04.9070606@oracle.com> Date: Wed, 10 Jul 2013 14:28:20 +0800 From: Jeff Liu MIME-Version: 1.0 Subject: Re: [PATCH] xfs: fix s_max_bytes to MAX_LFS_FILESIZE if needed References: <5167E160.3020800@oracle.com> In-Reply-To: <5167E160.3020800@oracle.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: "xfs@oss.sgi.com" Cc: "Michael L. Semon" Could anyone help to review this patch? Thanks, -Jeff On 04/12/2013 06:26 PM, Jeff Liu wrote: > From: Jie Liu > > On 32-bit machine, the s_maxbytes is larger than the MAX_LFS_FILESIZE limits if CONFIG_LBDAF is > not enabled. Hence it's possible to create a huge file via buffered-IO write with a given offset > beyond this limitation. e.g. > > # block_size=4096 > # offset=$(((2**32 - 1) * $block_size)) > # xfs_io -f -c "pwrite $offset $block_size" /storage/test_file > > In this case, xfs_io will hang at the page writeback stage soon since the given offset would > cause an overflow at xfs_vm_writepage(): > > end_index = offset >> PAGE_CACHE_SHIFT; > last_index = (offset - 1) >> PAGE_CACHE_SHIFT; > if (page->index >= end_index) { > unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1); > > /* > * Just skip the page if it is fully outside i_size, e.g. due > * to a truncate operation that is in progress. > */ > if (page->index >= end_index + 1 || offset_into_page == 0) { > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > unlock_page(page); > return 0; > } > end_index is unsigned long so that the max value is '2^32-1 = 4294967295', and it > would be evaluated to the max value with the given offset(when writing the page offset > up to s_max_bytes) for above test case. As a result, (page->index >= end_index + 1) is > ok as (end_index + 1) is overflowed to ZERO. > > Actually, create a file as above on 32-bit machine should be failed with EFBIG error returned > because there has strict check up at generic_write_checks() against the given offset with a > *correct* s_max_bytes. > > This patch fix the s_max_bytes to MAX_LFS_FILESIZE if the pre-calculated value is greater > than it. > > Reported-by: Michael L. Semon > Signed-off-by: Jie Liu > > --- > fs/xfs/xfs_super.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > index ea341ce..0644d61 100644 > --- a/fs/xfs/xfs_super.c > +++ b/fs/xfs/xfs_super.c > @@ -585,6 +585,7 @@ xfs_max_file_offset( > { > unsigned int pagefactor = 1; > unsigned int bitshift = BITS_PER_LONG - 1; > + __uint64_t offset; > > /* Figure out maximum filesize, on Linux this can depend on > * the filesystem blocksize (on 32 bit platforms). > @@ -610,7 +611,10 @@ xfs_max_file_offset( > # endif > #endif > > - return (((__uint64_t)pagefactor) << bitshift) - 1; > + offset = (((__uint64_t)pagefactor) << bitshift) - 1; > + > + /* Check against VM & VFS exposed limits */ > + return (offset > MAX_LFS_FILESIZE) ? MAX_LFS_FILESIZE : offset; > } > > xfs_agnumber_t _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs