[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.

Cc: Andrew Vasquez <andrew.vasquez@qlogic.com>
Cc: Ken Chen <kenchen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index d9bdf2b3ade2..fc7028b685f2 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -129,6 +129,46 @@ blkdev_get_block(struct inode *inode, sector_t iblock,
         return 0;
 }
 
+static int
+blkdev_get_blocks(struct inode *inode, sector_t iblock,
+                struct buffer_head *bh, int create)
+{
+        sector_t end_block = max_block(I_BDEV(inode));
+        unsigned long max_blocks = bh->b_size >> inode->i_blkbits;
+
+        if ((iblock + max_blocks) > end_block) {
+                max_blocks = end_block - iblock;
+                if ((long)max_blocks <= 0) {
+                        if (create)
+                                return -EIO;    /* write fully beyond EOF */
+                        /*
+                         * It is a read which is fully beyond EOF.  We return
+                         * a !buffer_mapped buffer
+                         */
+                        max_blocks = 0;
+                }
+        }
+
+        bh->b_bdev = I_BDEV(inode);
+        bh->b_blocknr = iblock;
+        bh->b_size = max_blocks << inode->i_blkbits;
+        if (max_blocks)
+                set_buffer_mapped(bh);
+        return 0;
+}
+
+static ssize_t
+blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
+                        loff_t offset, unsigned long nr_segs)
+{
+        struct file *file = iocb->ki_filp;
+        struct inode *inode = file->f_mapping->host;
+
+        return blockdev_direct_IO_no_locking(rw, iocb, inode, I_BDEV(inode),
+                                iov, offset, nr_segs, blkdev_get_blocks, NULL);
+}
+
+#if 0
 static int blk_end_aio(struct bio *bio, unsigned int bytes_done, int error)
 {
         struct kiocb *iocb = bio->bi_private;
@@ -323,6 +363,7 @@ backout:
                 return PTR_ERR(page);
         goto completion;
 }
+#endif
 
 static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
 {