Btrfs: allow unaligned DIO

In order to support DIO that isn't aligned to the filesystem blocksize,
we fall back to buffered for any unaligned DIOs.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5ab120d..6866c36 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5722,6 +5722,32 @@ free_ordered:
        bio_endio(bio, ret);
 }
 
+static ssize_t check_direct_IO(struct btrfs_root *root, int rw, struct kiocb *iocb,
+                       const struct iovec *iov, loff_t offset,
+                       unsigned long nr_segs)
+{
+       int seg;
+       size_t size;
+       unsigned long addr;
+       unsigned blocksize_mask = root->sectorsize - 1;
+       ssize_t retval = -EINVAL;
+       loff_t end = offset;
+
+       if (offset & blocksize_mask)
+               goto out;
+
+       /* Check the memory alignment.  Blocks cannot straddle pages */
+       for (seg = 0; seg < nr_segs; seg++) {
+               addr = (unsigned long)iov[seg].iov_base;
+               size = iov[seg].iov_len;
+               end += size;
+               if ((addr & blocksize_mask) || (size & blocksize_mask)) 
+                       goto out;
+       }
+       retval = 0;
+out:
+       return retval;
+}
 static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
                        const struct iovec *iov, loff_t offset,
                        unsigned long nr_segs)
@@ -5736,6 +5762,11 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
        int write_bits = 0;
        size_t count = iov_length(iov, nr_segs);
 
+       if (check_direct_IO(BTRFS_I(inode)->root, rw, iocb, iov,
+                           offset, nr_segs)) {
+               return 0;
+       }
+
        lockstart = offset;
        lockend = offset + count - 1;
 
@@ -5784,9 +5815,10 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
        free_extent_state(cached_state);
        cached_state = NULL;
 
-       ret = __blockdev_direct_IO(rw, iocb, inode, NULL, iov, offset, nr_segs,
-                                  btrfs_get_blocks_direct, NULL,
-                                  btrfs_submit_direct, 0);
+       ret = __blockdev_direct_IO(rw, iocb, inode,
+                  BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
+                  iov, offset, nr_segs, btrfs_get_blocks_direct, NULL,
+                  btrfs_submit_direct, 0);
 
        if (ret < 0 && ret != -EIOCBQUEUED) {
                clear_extent_bit(&BTRFS_I(inode)->io_tree, offset,