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([2406:7400:63:7035:9095:349e:5f0b:ded0]) by smtp.gmail.com with ESMTPSA id g8-20020aa78188000000b0063b23c92d02sm817243pfi.212.2023.04.13.01.41.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Apr 2023 01:41:18 -0700 (PDT) From: "Ritesh Harjani (IBM)" To: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org Cc: Jan Kara , Christoph Hellwig , "Darrick J . Wong" , Ojaswin Mujoo , Disha Goel , "Ritesh Harjani (IBM)" Subject: [RFCv3 01/10] ext2/dax: Fix ext2_setsize when len is page aligned Date: Thu, 13 Apr 2023 14:10:23 +0530 Message-Id: <895d3405f4831be6936f3df280792bff8cc2d401.1681365596.git.ritesh.list@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org PAGE_ALIGN(x) macro gives the next highest value which is multiple of pagesize. But if x is already page aligned then it simply returns x. So, if x passed is 0 in dax_zero_range() function, that means the length gets passed as 0 to ->iomap_begin(). In ext2 it then calls ext2_get_blocks -> max_blocks as 0 and hits bug_on here in ext2_get_blocks(). BUG_ON(maxblocks == 0); Instead we should be calling dax_truncate_page() here which takes care of it. i.e. it only calls dax_zero_range if the offset is not page/block aligned. This can be easily triggered with following on fsdax mounted pmem device. dd if=/dev/zero of=file count=1 bs=512 truncate -s 0 file [79.525838] EXT2-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk [79.529376] ext2 filesystem being mounted at /mnt1/test supports timestamps until 2038 (0x7fffffff) [93.793207] ------------[ cut here ]------------ [93.795102] kernel BUG at fs/ext2/inode.c:637! [93.796904] invalid opcode: 0000 [#1] PREEMPT SMP PTI [93.798659] CPU: 0 PID: 1192 Comm: truncate Not tainted 6.3.0-rc2-xfstests-00056-g131086faa369 #139 [93.806459] RIP: 0010:ext2_get_blocks.constprop.0+0x524/0x610 <...> [93.835298] Call Trace: [93.836253] [93.837103] ? lock_acquire+0xf8/0x110 [93.838479] ? d_lookup+0x69/0xd0 [93.839779] ext2_iomap_begin+0xa7/0x1c0 [93.841154] iomap_iter+0xc7/0x150 [93.842425] dax_zero_range+0x6e/0xa0 [93.843813] ext2_setsize+0x176/0x1b0 [93.845164] ext2_setattr+0x151/0x200 [93.846467] notify_change+0x341/0x4e0 [93.847805] ? lock_acquire+0xf8/0x110 [93.849143] ? do_truncate+0x74/0xe0 [93.850452] ? do_truncate+0x84/0xe0 [93.851739] do_truncate+0x84/0xe0 [93.852974] do_sys_ftruncate+0x2b4/0x2f0 [93.854404] do_syscall_64+0x3f/0x90 [93.855789] entry_SYSCALL_64_after_hwframe+0x72/0xdc Reviewed-by: Darrick J. Wong Signed-off-by: Ritesh Harjani (IBM) --- fs/ext2/inode.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c index 26f135e7ffce..dc76147e7b07 100644 --- a/fs/ext2/inode.c +++ b/fs/ext2/inode.c @@ -1259,9 +1259,8 @@ static int ext2_setsize(struct inode *inode, loff_t newsize) inode_dio_wait(inode); if (IS_DAX(inode)) - error = dax_zero_range(inode, newsize, - PAGE_ALIGN(newsize) - newsize, NULL, - &ext2_iomap_ops); + error = dax_truncate_page(inode, newsize, NULL, + &ext2_iomap_ops); else error = block_truncate_page(inode->i_mapping, newsize, ext2_get_block); -- 2.39.2