| Message ID | x49ehpbjiyp.fsf@segfault.boston.devel.redhat.com |
|---|---|
| State | Accepted, archived |
| Headers | show |
Am 19.06.2012 19:43, schrieb Jeff Moyer: [...] > diff --git a/fs/buffer.c b/fs/buffer.c > index 838a9cf..769b30b 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -930,7 +930,7 @@ init_page_buffers(struct page *page, struct block_device *bdev, > bh->b_blocknr = block; > if (uptodate) > set_buffer_uptodate(bh); > - if (block < end_block) > + if (block <= end_block) > set_buffer_mapped(bh); > } > block++; I can confirm that this patch fixes the problem for my test case too. Here is the kernel output when performing the mount operation: attempt to access beyond end of device sda4: rw=0, want=4, limit=2 EXT3-fs (sda4): error: unable to read superblock Torsten -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue 19-06-12 13:43:26, Jeff Moyer wrote: > Torsten Hilbrich <torsten.hilbrich@secunet.com> writes: > > > The system where I reproduced the problem upstream is an amd64 based > > ubuntu 12.04 installation. I used both v3.3.8 and v3.4 for reproducing. > > > > The partition layout is the following: > > > > ====================================================================== > > > > Disk /dev/sda: 120.0 GB, 120034123776 bytes > > 255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors > > Units = sectors of 1 * 512 = 512 bytes > > Sector size (logical/physical): 512 bytes / 512 bytes > > I/O size (minimum/optimal): 512 bytes / 512 bytes > > Disk identifier: 0x1669c708 > > > > Device Boot Start End Blocks Id System > > /dev/sda1 * 63 86285114 43142526 83 Linux > > /dev/sda2 216797175 234436544 8819685 82 Linux swap / Solaris > > /dev/sda3 86285115 87088364 401625 83 Linux > > /dev/sda4 87088426 216797174 64854374+ 5 Extended > > /dev/sda5 87088428 91104614 2008093+ 83 Linux > > /dev/sda6 91104678 216797174 62846248+ 8e Linux LVM > > > > Partition table entries are not in disk order > > OK, got it to reproduce, thanks for the info. The attached patch fixed > the problem for me. > > Note, though, that the patch doesn't make sense to me. blkdev_max_block > returns i_size_read(blkdev_inode) >> block_size. This should be the > *size* of the block device, not the max block. The code in > fs/block_device.c uses the return value in two different ways! > > static int > blkdev_get_block(struct inode *inode, sector_t iblock, > struct buffer_head *bh, int create) > { > if (iblock >= blkdev_max_block(I_BDEV(inode))) { > > Here, the return value from blkdev_max_block is interpreted as the size > of the device, so actually max_block + 1. > > static int > blkdev_get_blocks(struct inode *inode, sector_t iblock, > struct buffer_head *bh, int create) > { > sector_t end_block = blkdev_max_block(I_BDEV(inode)); > unsigned long max_blocks = bh->b_size >> inode->i_blkbits; > > if ((iblock + max_blocks) > end_block) { > > Here, the return value is treated as the maximum addressable block > number. Given the fact that I had to modify init_page_buffers to treat > the return value from blkdev_max_block as the maximum addressable block, > I clearly have something wrong with my logic. Nick, Jens, care to set > my head straight? I think it can have something to do with the fact that the partition size is not a multiple of 4k (i.e. expected block size)? BTW: blkdev_max_block() is a terrible name for something that intends to return size in blocks... Honza
Jan Kara <jack@suse.cz> writes: > I think it can have something to do with the fact that the partition size > is not a multiple of 4k (i.e. expected block size)? Ahh, yes. Except that ext3 sets the blocksize to 1k by default. However, I still can't explain why we don't get an error attempting to access beyond the end of the device. I'll keep digging on that. > BTW: blkdev_max_block() is a terrible name for something that intends to > return size in blocks... Fully agreed here, and I'll fix that up when I get my head completely wrapped around this one. Thanks for taking a look, Jan! -Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/buffer.c b/fs/buffer.c index 838a9cf..769b30b 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -930,7 +930,7 @@ init_page_buffers(struct page *page, struct block_device *bdev, bh->b_blocknr = block; if (uptodate) set_buffer_uptodate(bh); - if (block < end_block) + if (block <= end_block) set_buffer_mapped(bh); } block++;