Messages in this thread | | | Date | Wed, 27 Feb 2008 13:13:29 +0300 | From | Dmitri Monakhov <> | Subject | Re: [PATCH] mm: fix blkdev size calculation in generic_write_checks |
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On 15:49 Tue 26 Feb , Andrew Morton wrote: > On Wed, 15 Aug 2007 17:52:28 +0400 Dmitry Monakhov <dmonakhov@openvz.org> wrote: > > > Currently block device size calculated regardless its > > bd_block_size. This may result attempt to write outside > > block device if i_size not aligned to bdev->bd_block_size > > and result in EIO. > > > > #### TEST_CASE_BEGIN > > # fdisk -l /dev/sdc > > Disk /dev/sdc: 36.7 GB, 36703918080 bytes > > 255 heads, 63 sectors/track, 4462 cylinders > > Units = cylinders of 16065 * 512 = 8225280 bytes > > > > Device Boot Start End Blocks Id System > > /dev/sdc1 * 1 254 2040223+ 83 Ldinux > > /dev/sdc2 255 379 1004062+ 83 Linux > > #### > > #### /dev/sdc2 size not aligned to 4K > > > > #### at this time bd_block_size == 512 so generic_write_check > > #### performed correctly > > # dd if=/dev/zero of=/dev/sdc2 bs=1k count=7 seek=1004058 > > dd: writing `/dev/sdc2': No space left on device > > 5+0 records in > > 4+0 records out > > > > #### this bdev contain ext4fs with blksize = 4K > > # mount /dev/sdc2 /mnt/ > > #### after we mounted this bdev bd_block_size == fsblksize == 4K > > > > #### the same write operation failed with EIO > > # dd if=/dev/zero of=/dev/sdc2 bs=1k count=7 seek=1004058 > > dd: writing `/dev/sdc2': Input/output error > > 3+0 records in > > 2+0 records out > > #### Attempt to write whole fsblock result write access outside > > #### blkdevice and cause -EIO (returned by blkdev_get_block) > > #### TEST_CASE_END > > > > Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> > > --- > > mm/filemap.c | 4 +++- > > 1 files changed, 3 insertions(+), 1 deletions(-) > > > > diff --git a/mm/filemap.c b/mm/filemap.c > > index 2c8776b..a23ee8a 100644 > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -1867,9 +1867,11 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i > > } else { > > #ifdef CONFIG_BLOCK > > loff_t isize; > > + unsigned int blksize; > > if (bdev_read_only(I_BDEV(inode))) > > return -EPERM; > > - isize = i_size_read(inode); > > + blksize = block_size(I_BDEV(inode)); > > + isize = i_size_read(inode) & ~(blksize - 1); > > if (*pos >= isize) { > > if (*count || *pos > isize) > > return -ENOSPC; > > I'm trying to work out how the heck we fixed In fact original issue (wich was reported by me) stil exist # uname -a Linux ts52 2.6.25-rc3 #8 SMP Wed Feb 27 11:41:29 MSK 2008 x86_64 x86_64 x86_64 GNU/Linux # blockdev --getsz /dev/sda7 208782 # blockdev --getbsz /dev/sda7 4096 # dd if=/dev/zero of=/dev/sda7 bs=1k seek=104390 count=1 dd: writing `/dev/sda7': Input/output error 1+0 records in 0+0 records out 0 bytes (0 B) copied, 0.000918887 seconds, 0.0 kB/s
This issue triggered in blkdev_get_block(), which is VFS layer
> http://bugzilla.kernel.org/show_bug.cgi?id=10116 Issue from the bug was triggered in __generic_make_request() ->bio_check_eod() ->handle_bad_sector() ###Bug's log: Feb 26 19:17:25 tux attempt to access beyond end of device Feb 26 19:17:25 tux sr0: rw=0, want=4911744, limit=2097151 ###Corresponding code: printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n", bdevname(bio->bi_bdev, b), bio->bi_rw, (unsigned long long)bio->bi_sector + bio_sectors(bio), (long long)(bio->bi_bdev->bd_inode->i_size >> 9)); This means that all vfs checks was already done (iblock >=max_block(I_BDEV(inode))) was TRUE at this time. But during __generic_make_request() we have found what "want" was more whan x2 times biger than "limit". IMHO: this may happens because of bug in DVD driver itself. > > We never merged your patch because it introduced problems. But did we > merge some alternative fix, or does the bug remain in there? >
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