From: Ritesh Harjani (IBM) ritesh.list@gmail.com
commit fcced95b6ba2a507a83b8b3e0358a8ac16b13e35 upstream.
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] <TASK> [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
CC: stable@vger.kernel.org Fixes: 2aa3048e03d3 ("iomap: switch iomap_zero_range to use iomap_iter") Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Ritesh Harjani (IBM) ritesh.list@gmail.com Signed-off-by: Jan Kara jack@suse.cz Message-Id: 046a58317f29d9603d1068b2bbae47c2332c17ae.1682069716.git.ritesh.list@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext2/inode.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/fs/ext2/inode.c +++ b/fs/ext2/inode.c @@ -1265,9 +1265,8 @@ static int ext2_setsize(struct inode *in 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);