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>

1 files changed, 35 insertions, 3 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5ab120d544bc..6866c36c26fb 100644
--- 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,