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authorAkinobu Mita <akinobu.mita@gmail.com>2014-10-09 15:26:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-09 22:25:53 -0400
commit59d43914ed7b96255271ad6b7b735344beffa3c0 (patch)
tree83497d5e1b25c77fc222d5845b584c258857fde5
parent21bb9bd19430a43e6462ce75030fd7fac4b766ef (diff)
vfs: make guard_bh_eod() more generic
This patchset implements readpages() operation for block device by using mpage_readpages() which can create multipage BIOs instead of BIOs for each page and reduce system CPU time consumption. This patch (of 3): 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 <akinobu.mita@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/buffer.c26
1 files changed, 12 insertions, 14 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 3588a80854b2..e442a26e80f7 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2956,7 +2956,7 @@ 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,
@@ -2966,10 +2966,11 @@ 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)
@@ -2984,23 +2985,20 @@ 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);
}
}
@@ -3041,7 +3039,7 @@ 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;