[RFC: 2.6 patch] fs/block_dev.c: remove #if 0'ed code

From: Adrian Bunk
Date: Sun Feb 17 2008 - 03:19:58 EST

Commit b2e895dbd80c420bfc0937c3729b4afe073b3848 #if 0'ed this code stating:

<-- snip -->

[PATCH] revert blockdev direct io back to 2.6.19 version

Andrew Vasquez is reporting as-iosched oopses and a 65% throughput
slowdown due to the recent special-casing of direct-io against
blockdevs. We don't know why either of these things are occurring.

The patch minimally reverts us back to the 2.6.19 code for a 2.6.20
release.

<-- snip -->

It has since been dead code, and unless someone wants to revive it now
it's time to remove it.

This patch also makes bio_release_pages() static again and removes the
ki_bio_count member from struct kiocb, reverting changes that had been
done for this dead code.

Signed-off-by: Adrian Bunk <bunk@xxxxxxxxxx>

---

fs/bio.c | 2
fs/block_dev.c | 197 --------------------------------------------
include/linux/aio.h | 1
include/linux/bio.h | 1
4 files changed, 1 insertion(+), 200 deletions(-)

ba8404ffaa1d5a509f7e783f15dbf0d8c827fa85 diff --git a/fs/bio.c b/fs/bio.c
index 242e409..3312fcc 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -903,7 +903,7 @@ void bio_set_pages_dirty(struct bio *bio)
}
}

-void bio_release_pages(struct bio *bio)
+static void bio_release_pages(struct bio *bio)
{
struct bio_vec *bvec = bio->bi_io_vec;
int i;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 8335f0e..7d822fa 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -173,203 +173,6 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
iov, offset, nr_segs, blkdev_get_blocks, NULL);
}

-#if 0
-static void blk_end_aio(struct bio *bio, int error)
-{
- struct kiocb *iocb = bio->bi_private;
- atomic_t *bio_count = &iocb->ki_bio_count;
-
- if (bio_data_dir(bio) == READ)
- bio_check_pages_dirty(bio);
- else {
- bio_release_pages(bio);
- bio_put(bio);
- }
-
- /* iocb->ki_nbytes stores error code from LLDD */
- if (error)
- iocb->ki_nbytes = -EIO;
-
- if (atomic_dec_and_test(bio_count)) {
- if ((long)iocb->ki_nbytes < 0)
- aio_complete(iocb, iocb->ki_nbytes, 0);
- else
- aio_complete(iocb, iocb->ki_left, 0);
- }
-
- return 0;
-}
-
-#define VEC_SIZE 16
-struct pvec {
- unsigned short nr;
- unsigned short idx;
- struct page *page[VEC_SIZE];
-};
-
-#define PAGES_SPANNED(addr, len) \
- (DIV_ROUND_UP((addr) + (len), PAGE_SIZE) - (addr) / PAGE_SIZE);
-
-/*
- * get page pointer for user addr, we internally cache struct page array for
- * (addr, count) range in pvec to avoid frequent call to get_user_pages. If
- * internal page list is exhausted, a batch count of up to VEC_SIZE is used
- * to get next set of page struct.
- */
-static struct page *blk_get_page(unsigned long addr, size_t count, int rw,
- struct pvec *pvec)
-{
- int ret, nr_pages;
- if (pvec->idx == pvec->nr) {
- nr_pages = PAGES_SPANNED(addr, count);
- nr_pages = min(nr_pages, VEC_SIZE);
- down_read(&current->mm->mmap_sem);
- ret = get_user_pages(current, current->mm, addr, nr_pages,
- rw == READ, 0, pvec->page, NULL);
- up_read(&current->mm->mmap_sem);
- if (ret < 0)
- return ERR_PTR(ret);
- pvec->nr = ret;
- pvec->idx = 0;
- }
- return pvec->page[pvec->idx++];
-}
-
-/* return a page back to pvec array */
-static void blk_unget_page(struct page *page, struct pvec *pvec)
-{
- pvec->page[--pvec->idx] = page;
-}
-
-static ssize_t
-blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
- loff_t pos, unsigned long nr_segs)
-{
- struct inode *inode = iocb->ki_filp->f_mapping->host;
- unsigned blkbits = blksize_bits(bdev_hardsect_size(I_BDEV(inode)));
- unsigned blocksize_mask = (1 << blkbits) - 1;
- unsigned long seg = 0; /* iov segment iterator */
- unsigned long nvec; /* number of bio vec needed */
- unsigned long cur_off; /* offset into current page */
- unsigned long cur_len; /* I/O len of current page, up to PAGE_SIZE */
-
- unsigned long addr; /* user iovec address */
- size_t count; /* user iovec len */
- size_t nbytes = iocb->ki_nbytes = iocb->ki_left; /* total xfer size */
- loff_t size; /* size of block device */
- struct bio *bio;
- atomic_t *bio_count = &iocb->ki_bio_count;
- struct page *page;
- struct pvec pvec;
-
- pvec.nr = 0;
- pvec.idx = 0;
-
- if (pos & blocksize_mask)
- return -EINVAL;
-
- size = i_size_read(inode);
- if (pos + nbytes > size) {
- nbytes = size - pos;
- iocb->ki_left = nbytes;
- }
-
- /*
- * check first non-zero iov alignment, the remaining
- * iov alignment is checked inside bio loop below.
- */
- do {
- addr = (unsigned long) iov[seg].iov_base;
- count = min(iov[seg].iov_len, nbytes);
- if (addr & blocksize_mask || count & blocksize_mask)
- return -EINVAL;
- } while (!count && ++seg < nr_segs);
- atomic_set(bio_count, 1);
-
- while (nbytes) {
- /* roughly estimate number of bio vec needed */
- nvec = (nbytes + PAGE_SIZE - 1) / PAGE_SIZE;
- nvec = max(nvec, nr_segs - seg);
- nvec = min(nvec, (unsigned long) BIO_MAX_PAGES);
-
- /* bio_alloc should not fail with GFP_KERNEL flag */
- bio = bio_alloc(GFP_KERNEL, nvec);
- bio->bi_bdev = I_BDEV(inode);
- bio->bi_end_io = blk_end_aio;
- bio->bi_private = iocb;
- bio->bi_sector = pos >> blkbits;
-same_bio:
- cur_off = addr & ~PAGE_MASK;
- cur_len = PAGE_SIZE - cur_off;
- if (count < cur_len)
- cur_len = count;
-
- page = blk_get_page(addr, count, rw, &pvec);
- if (unlikely(IS_ERR(page)))
- goto backout;
-
- if (bio_add_page(bio, page, cur_len, cur_off)) {
- pos += cur_len;
- addr += cur_len;
- count -= cur_len;
- nbytes -= cur_len;
-
- if (count)
- goto same_bio;
- while (++seg < nr_segs) {
- addr = (unsigned long) iov[seg].iov_base;
- count = iov[seg].iov_len;
- if (!count)
- continue;
- if (unlikely(addr & blocksize_mask ||
- count & blocksize_mask)) {
- page = ERR_PTR(-EINVAL);
- goto backout;
- }
- count = min(count, nbytes);
- goto same_bio;
- }
- } else {
- blk_unget_page(page, &pvec);
- }
-
- /* bio is ready, submit it */
- if (rw == READ)
- bio_set_pages_dirty(bio);
- atomic_inc(bio_count);
- submit_bio(rw, bio);
- }
-
-completion:
- iocb->ki_left -= nbytes;
- nbytes = iocb->ki_left;
- iocb->ki_pos += nbytes;
-
- blk_run_address_space(inode->i_mapping);
- if (atomic_dec_and_test(bio_count))
- aio_complete(iocb, nbytes, 0);
-
- return -EIOCBQUEUED;
-
-backout:
- /*
- * back out nbytes count constructed so far for this bio,
- * we will throw away current bio.
- */
- nbytes += bio->bi_size;
- bio_release_pages(bio);
- bio_put(bio);
-
- /*
- * if no bio was submmitted, return the error code.
- * otherwise, proceed with pending I/O completion.
- */
- if (atomic_read(bio_count) == 1)
- return PTR_ERR(page);
- goto completion;
-}
-#endif
-
static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
{
return block_write_full_page(page, blkdev_get_block, wbc);
diff --git a/include/linux/aio.h b/include/linux/aio.h
index cf0f82b..b51ddd2 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -105,7 +105,6 @@ struct kiocb {
wait_queue_t ki_wait;
loff_t ki_pos;

- atomic_t ki_bio_count; /* num bio used for this iocb */
void *private;
/* State that we remember to be able to restart/retry */
unsigned short ki_opcode;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 4da4413..4c59bdc 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -326,7 +326,6 @@ extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
gfp_t);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(struct bio *bio);
-extern void bio_release_pages(struct bio *bio);
extern struct bio *bio_copy_user(struct request_queue *, unsigned long, unsigned int, int);
extern int bio_uncopy_user(struct bio *);
void zero_fill_bio(struct bio *bio);

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