[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>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index d9bdf2b..fc7028b 100644 (file)
--- 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)
 {