Messages in this thread Patch in this message |  | | Date | Mon, 10 Dec 2001 12:59:32 +0900 | From | GOTO Masanori <> | Subject | Re: [PATCH] direct IO breaks root filesystem |
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Hi,
Kernel both 2.4.16-pre7 and 2.5.1-pre8 have serious problem when we use direct IO for the block device. These kernel breaks my root filesystem which has /dev (block device entry) when an application like dd write data into /dev/sdXX (= not root filesystem's device).
My environment is: /dev/hda root filesystem with /dev/ dir. /dev/sda target direct io device I lost my root filesystem with: fd = open("/dev/sda", O_DIRECT); write(fd, data, large_size);
The reason is that when kernel accesses /dev/sda with O_DIRECT, blkdev_direct_IO() is called. But, it calls generic_direct_IO(), and generic_direct_IO() calls brw_kiovec(..., inode->i_dev, ...). If inode->i_dev is root filesystem, not target direct io device, then inode->i_dev is used for root filesystem overwriting (= then I lost my root file system...).
Here is patch, it was based some parts in 2.4.10 (and some 2.4.1x-aa). In my test with this patch, it works well and kernel does not break my root partition.
Linus and Marcelo, please apply this patch.
-- gotom
--- fs/block_dev.c.vanilla Sat Dec 8 22:46:15 2001 +++ fs/block_dev.c Mon Dec 10 10:45:20 2001 @@ -115,7 +115,25 @@ static int blkdev_direct_IO(int rw, struct inode * inode, struct kiobuf * iobuf, unsigned long blocknr, int blocksize) { - return generic_direct_IO(rw, inode, iobuf, blocknr, blocksize, blkdev_get_block); + int i, nr_blocks, retval; + unsigned long * blocks = iobuf->blocks; + + nr_blocks = iobuf->length / blocksize; + /* build the blocklist */ + for (i = 0; i < nr_blocks; i++, blocknr++) { + struct buffer_head bh; + + retval = blkdev_get_block(inode, blocknr, &bh, 0); + if (retval) + goto out; + + blocks[i] = bh.b_blocknr; + } + + retval = brw_kiovec(rw, 1, &iobuf, inode->i_rdev, iobuf->blocks, blocksize); + + out: + return retval; } static int blkdev_writepage(struct page * page) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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