new primitive: iov_iter_alignment()

returns the value aligned as badly as the worst remaining segment
in iov_iter is.  Use instead of open-coded equivalents.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 22 deletions

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 1c677899b989..adfa1fb33456 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1112,19 +1112,18 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
         dio_submit_t submit_io, int flags)
 {
         int seg;
-        size_t size;
-        unsigned long addr;
         unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
         unsigned blkbits = i_blkbits;
         unsigned blocksize_mask = (1 << blkbits) - 1;
         ssize_t retval = -EINVAL;
-        loff_t end = offset;
+        loff_t end = offset + iov_iter_count(iter);
         struct dio *dio;
         struct dio_submit sdio = { 0, };
         unsigned long user_addr;
         size_t bytes;
         struct buffer_head map_bh = { 0, };
         struct blk_plug plug;
+        unsigned long align = offset | iov_iter_alignment(iter);
 
         if (rw & WRITE)
                 rw = WRITE_ODIRECT;
@@ -1134,32 +1133,16 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
          * the early prefetch in the caller enough time.
          */
 
-        if (offset & blocksize_mask) {
+        if (align & blocksize_mask) {
                 if (bdev)
                         blkbits = blksize_bits(bdev_logical_block_size(bdev));
                 blocksize_mask = (1 << blkbits) - 1;
-                if (offset & blocksize_mask)
+                if (align & blocksize_mask)
                         goto out;
         }
 
-        /* Check the memory alignment.  Blocks cannot straddle pages */
-        for (seg = 0; seg < iter->nr_segs; seg++) {
-                addr = (unsigned long)iter->iov[seg].iov_base;
-                size = iter->iov[seg].iov_len;
-                end += size;
-                if (unlikely((addr & blocksize_mask) ||
-                             (size & blocksize_mask))) {
-                        if (bdev)
-                                blkbits = blksize_bits(
-                                         bdev_logical_block_size(bdev));
-                        blocksize_mask = (1 << blkbits) - 1;
-                        if ((addr & blocksize_mask) || (size & blocksize_mask))
-                                goto out;
-                }
-        }
-
         /* watch out for a 0 len io from a tricksy fs */
-        if (rw == READ && end == offset)
+        if (rw == READ && !iov_iter_count(iter))
                 return 0;
 
         dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);