2 files changed, 23 insertions, 16 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9dfd7c7ff8e3..87be51aff9d7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -48,6 +48,7 @@ struct cred;
 struct swap_info_struct;
 struct seq_file;
 struct workqueue_struct;
+struct iov_iter;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -2396,6 +2397,7 @@ extern ssize_t __generic_file_aio_write(struct kiocb *, const struct iovec *, un
 extern ssize_t generic_file_aio_write(struct kiocb *, const struct iovec *, unsigned long, loff_t);
 extern ssize_t generic_file_direct_write(struct kiocb *, const struct iovec *,
                 unsigned long *, loff_t, size_t, size_t);
+extern ssize_t generic_perform_write(struct file *, struct iov_iter *, loff_t);
 extern ssize_t generic_file_buffered_write(struct kiocb *, const struct iovec *,
                 unsigned long, loff_t, size_t, ssize_t);
 extern ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
diff --git a/mm/filemap.c b/mm/filemap.c
index 93e9cf576452..09bfc9b3bb51 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2092,7 +2092,7 @@ found:
 }
 EXPORT_SYMBOL(grab_cache_page_write_begin);
 
-static ssize_t generic_perform_write(struct file *file,
+ssize_t generic_perform_write(struct file *file,
                                 struct iov_iter *i, loff_t pos)
 {
         struct address_space *mapping = file->f_mapping;
@@ -2180,6 +2180,7 @@ again:
 
         return written ? written : status;
 }
+EXPORT_SYMBOL(generic_perform_write);
 
 ssize_t
 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
@@ -2230,8 +2231,10 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
         size_t count;           /* after file limit checks */
         struct inode    *inode = mapping->host;
         loff_t          pos = iocb->ki_pos;
-        ssize_t         written;
+        ssize_t         written = 0;
         ssize_t         err;
+        ssize_t         status;
+        struct iov_iter from;
 
         ocount = 0;
         err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
@@ -2242,8 +2245,6 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
 
         /* We can write back this queue in page reclaim */
         current->backing_dev_info = mapping->backing_dev_info;
-        written = 0;
-
         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
         if (err)
                 goto out;
@@ -2259,44 +2260,47 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
         if (err)
                 goto out;
 
+        iov_iter_init(&from, iov, nr_segs, count, 0);
+
         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
         if (unlikely(file->f_flags & O_DIRECT)) {
                 loff_t endbyte;
-                ssize_t written_buffered;
 
-                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
+                written = generic_file_direct_write(iocb, iov, &from.nr_segs, pos,
                                                         count, ocount);
                 if (written < 0 || written == count)
                         goto out;
+                iov_iter_advance(&from, written);
+
                 /*
                  * direct-io write to a hole: fall through to buffered I/O
                  * for completing the rest of the request.
                  */
                 pos += written;
                 count -= written;
-                written_buffered = generic_file_buffered_write(iocb, iov,
-                                                nr_segs, pos, count, written);
+
+                status = generic_perform_write(file, &from, pos);
                 /*
-                 * If generic_file_buffered_write() retuned a synchronous error
+                 * If generic_perform_write() returned a synchronous error
                  * then we want to return the number of bytes which were
                  * direct-written, or the error code if that was zero.  Note
                  * that this differs from normal direct-io semantics, which
                  * will return -EFOO even if some bytes were written.
                  */
-                if (written_buffered < 0) {
-                        err = written_buffered;
+                if (unlikely(status < 0) && !written) {
+                        err = status;
                         goto out;
                 }
-
+                iocb->ki_pos = pos + status;
                 /*
                  * We need to ensure that the page cache pages are written to
                  * disk and invalidated to preserve the expected O_DIRECT
                  * semantics.
                  */
-                endbyte = pos + written_buffered - written - 1;
+                endbyte = pos + status - 1;
                 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
                 if (err == 0) {
-                        written = written_buffered;
+                        written += status;
                         invalidate_mapping_pages(mapping,
                                                  pos >> PAGE_CACHE_SHIFT,
                                                  endbyte >> PAGE_CACHE_SHIFT);
@@ -2307,8 +2311,9 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
                          */
                 }
         } else {
-                written = generic_file_buffered_write(iocb, iov, nr_segs,
-                                pos, count, written);
+                written = generic_perform_write(file, &from, pos);
+                if (likely(written >= 0))
+                        iocb->ki_pos = pos + written;
         }
 out:
         current->backing_dev_info = NULL;