diff options
| -rw-r--r-- | fs/buffer.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 3586fb0..c4e1139 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2893,6 +2893,55 @@ static void end_bio_bh_io_sync(struct bio *bio, int err) bio_put(bio); } +/* + * 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 the physical sector size. + * + * We'll just truncate the bio to the size of the device, + * and clear the end of the buffer head manually. + * + * Truly out-of-range accesses will turn into actual IO + * 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) +{ + sector_t maxsector; + unsigned bytes; + + maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; + if (!maxsector) + return; + + /* + * If the *whole* IO is past the end of the device, + * let it through, and the IO layer will turn it into + * an EIO. + */ + if (unlikely(bio->bi_sector >= maxsector)) + return; + + maxsector -= bio->bi_sector; + bytes = bio->bi_size; + if (likely((bytes >> 9) <= maxsector)) + return; + + /* Uhhuh. We've got a bh that straddles the device size! */ + bytes = maxsector << 9; + + /* Truncate the bio.. */ + bio->bi_size = bytes; + bio->bi_io_vec[0].bv_len = bytes; + + /* ..and clear the end of the buffer for reads */ + if (rw & READ) { + void *kaddr = kmap_atomic(bh->b_page); + memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes); + kunmap_atomic(kaddr); + } +} + int submit_bh(int rw, struct buffer_head * bh) { struct bio *bio; @@ -2929,6 +2978,9 @@ int submit_bh(int rw, struct buffer_head * bh) bio->bi_end_io = end_bio_bh_io_sync; bio->bi_private = bh; + /* Take care of bh's that straddle the end of the device */ + guard_bh_eod(rw, bio, bh); + bio_get(bio); submit_bio(rw, bio); |
