guard_bh_eod() is used in submit_bh() to allow us to do IO even on the odd last sectors of a device, even if the block size is some multiple of the physical sector size. This makes guard_bh_eod() more generic and renames it guard_bio_eod() so that we can use it without struct buffer_head argument.
The reason for this change is that using mpage_readpages() for block device requires to add this guard check in mpage code. Signed-off-by: Akinobu Mita <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Jens Axboe <[email protected]> Cc: Alexander Viro <[email protected]> Cc: Jeff Moyer <[email protected]> Cc: [email protected] --- fs/buffer.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 8f05111..f891c90 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2954,7 +2954,7 @@ static void end_bio_bh_io_sync(struct bio *bio, int err) /* * This allows us to do IO even on the odd last sectors - * of a device, even if the bh block size is some multiple + * of a device, even if the block size is some multiple * of the physical sector size. * * We'll just truncate the bio to the size of the device, @@ -2964,10 +2964,11 @@ static void end_bio_bh_io_sync(struct bio *bio, int err) * errors, this only handles the "we need to be able to * do IO at the final sector" case. */ -static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh) +static void guard_bio_eod(int rw, struct bio *bio) { sector_t maxsector; - unsigned bytes; + struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1]; + unsigned truncated_bytes; maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; if (!maxsector) @@ -2982,23 +2983,20 @@ static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh) return; maxsector -= bio->bi_iter.bi_sector; - bytes = bio->bi_iter.bi_size; - if (likely((bytes >> 9) <= maxsector)) + if (likely((bio->bi_iter.bi_size >> 9) <= maxsector)) return; - /* Uhhuh. We've got a bh that straddles the device size! */ - bytes = maxsector << 9; + /* Uhhuh. We've got a bio that straddles the device size! */ + truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9); /* Truncate the bio.. */ - bio->bi_iter.bi_size = bytes; - bio->bi_io_vec[0].bv_len = bytes; + bio->bi_iter.bi_size -= truncated_bytes; + bvec->bv_len -= truncated_bytes; /* ..and clear the end of the buffer for reads */ if ((rw & RW_MASK) == READ) { - void *kaddr = kmap_atomic(bh->b_page); - memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes); - kunmap_atomic(kaddr); - flush_dcache_page(bh->b_page); + zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len, + truncated_bytes); } } @@ -3039,7 +3037,7 @@ int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags) bio->bi_flags |= bio_flags; /* Take care of bh's that straddle the end of the device */ - guard_bh_eod(rw, bio, bh); + guard_bio_eod(rw, bio); if (buffer_meta(bh)) rw |= REQ_META; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
