mm: write iovec cleanup

Hide some of the open-coded nr_segs tests into the iovec helpers.  This is all
to simplify generic_file_buffered_write, because that gets more complex in the
next patch.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 26 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index fb4c1c0792e7..c59d5b3cd99a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1823,12 +1823,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
         /*
          * handle partial DIO write.  Adjust cur_iov if needed.
          */
-        if (likely(nr_segs == 1))
-                buf = iov->iov_base + written;
-        else {
-                filemap_set_next_iovec(&cur_iov, &iov_offset, written);
-                buf = cur_iov->iov_base + iov_offset;
-        }
+        filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, written);
 
         do {
                 struct page *page;
@@ -1838,6 +1833,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
                 size_t bytes;           /* Bytes to write to page */
                 size_t copied;          /* Bytes copied from user */
 
+                buf = cur_iov->iov_base + iov_offset;
                 offset = (pos & (PAGE_CACHE_SIZE - 1));
                 index = pos >> PAGE_CACHE_SHIFT;
                 bytes = PAGE_CACHE_SIZE - offset;
@@ -1869,13 +1865,10 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
                 if (unlikely(status))
                         goto fs_write_aop_error;
 
-                if (likely(nr_segs == 1))
-                        copied = filemap_copy_from_user(page, offset,
-                                                        buf, bytes);
-                else
-                        copied = filemap_copy_from_user_iovec(page, offset,
-                                                cur_iov, iov_offset, bytes);
+                copied = filemap_copy_from_user(page, offset,
+                                        cur_iov, nr_segs, iov_offset, bytes);
                 flush_dcache_page(page);
+
                 status = a_ops->commit_write(file, page, offset, offset+bytes);
                 if (unlikely(status < 0 || status == AOP_TRUNCATED_PAGE))
                         goto fs_write_aop_error;
@@ -1886,20 +1879,11 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
                 if (unlikely(status > 0)) /* filesystem did partial write */
                         copied = status;
 
-                if (likely(copied > 0)) {
-                        written += copied;
-                        count -= copied;
-                        pos += copied;
-                        buf += copied;
-                        if (unlikely(nr_segs > 1)) {
-                                filemap_set_next_iovec(&cur_iov,
-                                                &iov_offset, copied);
-                                if (count)
-                                        buf = cur_iov->iov_base + iov_offset;
-                        } else {
-                                iov_offset += copied;
-                        }
-                }
+                written += copied;
+                count -= copied;
+                pos += copied;
+                filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, copied);
+
                 unlock_page(page);
                 mark_page_accessed(page);
                 page_cache_release(page);