The patch titled
Subject: vfs: make guard_bh_eod() more generic
has been added to the -mm tree. Its filename is
vfs-make-guard_bh_eod-more-generic.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/vfs-make-guard_bh_eod-more-generic.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/vfs-make-guard_bh_eod-more-generic.patch
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------------------------------------------------------
From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Subject: 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@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/buffer.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
diff -puN fs/buffer.c~vfs-make-guard_bh_eod-more-generic fs/buffer.c
--- a/fs/buffer.c~vfs-make-guard_bh_eod-more-generic
+++ a/fs/buffer.c
@@ -2954,7 +2954,7 @@ static void end_bio_bh_io_sync(struct bi
/*
* 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 bi
* 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
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_hea
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;
_
Patches currently in -mm which might be from akinobu.mita@xxxxxxxxx are
vfs-make-guard_bh_eod-more-generic.patch
vfs-guard-end-of-device-for-mpage-interface.patch
block_dev-implement-readpages-to-optimize-sequential-read.patch
linux-next.patch
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