Messages in this thread Patch in this message | | | Date | Tue, 11 Dec 2001 18:03:08 +0900 | From | GOTO Masanori <> | Subject | Re: [PATCH] direct IO breaks root filesystem |
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At Mon, 10 Dec 2001 09:10:24 -0800 (PST), Linus Torvalds <torvalds@transmeta.com> wrote: > On Mon, 10 Dec 2001, GOTO Masanori wrote: > > > > > > "generic_direct_IO()" should just get the device from "bh->b_dev (which is > > > filled in correctly by "get_block()". > > > > Oh, that's right, the patch becomes more simple (and works well). > > Is this patch OK?
Linus, Andrea, thank you for your comments!
> This looks fine to me. At some point we _may_ end up with filesystems that > understand about multiple devices, so it's possible in theory that > "get_block()" might return different devices for different blocks, but > that does not happen currently, and I'm not really sure it ever will.
I don't test for the multiple device with direct IO under current kernel..., I keep it in mind.
> Marcelo, I do believe this should go into 2.4.x too..
Thanks Marcelo for including my patch :)
I, however, found another problem. Accessing with inode size unit (== 4096 byte) is ok, but if I accessed with block size unit, generic_direct_IO() returns error. The reason is that blocksize is designated as inode->i_blkbits, and its value is not disk minimal block size (512), but inode's unit size (4096).
Patch is here. If inode is S_ISBLK and is not mounted, then blocksize is set as hardsect_size. This implementation needs some computational cost, but I think it can be ignored. This patch works well for me.
--- linux-2.4.17-pre8.vanilla/mm/filemap.c Tue Dec 11 15:54:57 2001 +++ linux-2.4.17-pre8/mm/filemap.c Tue Dec 11 16:21:40 2001 @@ -1508,8 +1508,22 @@ new_iobuf = 1; } - blocksize = 1 << inode->i_blkbits; - blocksize_bits = inode->i_blkbits; + /* + * If inode is BLK and it is not already mounted, + * blocksize change hardsect_size. + */ + if (S_ISBLK(inode->i_mode) && !is_mounted(inode->i_rdev)) { + int size; + + size = get_hardsect_size(inode->i_rdev); + blocksize = size; + for (blocksize_bits = 0; !(size & 1); ) + size >>= 1, blocksize_bits++; + } else { + blocksize = 1 << inode->i_blkbits; + blocksize_bits = inode->i_blkbits; + } + blocksize_mask = blocksize - 1; chunk_size = KIO_MAX_ATOMIC_IO << 10;
The current problem is that is_mounted() checking is worked for /dev/sda1 (partition area) only, not for /dev/sda (total disk area), if /dev/sda1 is mounted. This problem is also existed in /dev/raw interface, but I think it's not important issue (should I fix it?)
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