1 files changed, 65 insertions, 4 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 6d8f817eadb5..a28810abfb98 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -822,6 +822,47 @@ again:
         return 0;
 }
 
+/* Copied from read-write.c */
+static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
+{
+        set_current_state(TASK_UNINTERRUPTIBLE);
+        if (!kiocbIsKicked(iocb))
+                schedule();
+        else
+                kiocbClearKicked(iocb);
+        __set_current_state(TASK_RUNNING);
+}
+
+/*
+ * Just a copy of what do_sync_write does.
+ */
+static ssize_t __btrfs_direct_write(struct file *file, const char __user *buf,
+                                    size_t count, loff_t pos, loff_t *ppos)
+{
+        struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
+        unsigned long nr_segs = 1;
+        struct kiocb kiocb;
+        ssize_t ret;
+
+        init_sync_kiocb(&kiocb, file);
+        kiocb.ki_pos = pos;
+        kiocb.ki_left = count;
+        kiocb.ki_nbytes = count;
+
+        while (1) {
+                ret = generic_file_direct_write(&kiocb, &iov, &nr_segs, pos,
+                                                ppos, count, count);
+                if (ret != -EIOCBRETRY)
+                        break;
+                wait_on_retry_sync_kiocb(&kiocb);
+        }
+
+        if (ret == -EIOCBQUEUED)
+                ret = wait_on_sync_kiocb(&kiocb);
+        *ppos = kiocb.ki_pos;
+        return ret;
+}
+
 static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                                 size_t count, loff_t *ppos)
 {
@@ -838,12 +879,11 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         unsigned long first_index;
         unsigned long last_index;
         int will_write;
+        int buffered = 0;
 
         will_write = ((file->f_flags & O_DSYNC) || IS_SYNC(inode) ||
                       (file->f_flags & O_DIRECT));
 
-        nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
-                     PAGE_CACHE_SIZE / (sizeof(struct page *)));
         pinned[0] = NULL;
         pinned[1] = NULL;
 
@@ -867,13 +907,34 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 goto out;
 
         file_update_time(file);
+        BTRFS_I(inode)->sequence++;
+
+        if (unlikely(file->f_flags & O_DIRECT)) {
+                num_written = __btrfs_direct_write(file, buf, count, pos,
+                                                   ppos);
+                pos += num_written;
+                count -= num_written;
+
+                /* We've written everything we wanted to, exit */
+                if (num_written < 0 || !count)
+                        goto out;
 
+                /*
+                 * We are going to do buffered for the rest of the range, so we
+                 * need to make sure to invalidate the buffered pages when we're
+                 * done.
+                 */
+                buffered = 1;
+                buf += num_written;
+        }
+
+        nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
+                     PAGE_CACHE_SIZE / (sizeof(struct page *)));
         pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
 
         /* generic_write_checks can change our pos */
         start_pos = pos;
 
-        BTRFS_I(inode)->sequence++;
         first_index = pos >> PAGE_CACHE_SHIFT;
         last_index = (pos + count) >> PAGE_CACHE_SHIFT;
 
@@ -1007,7 +1068,7 @@ out:
                                 btrfs_end_transaction(trans, root);
                         }
                 }
-                if (file->f_flags & O_DIRECT) {
+                if (file->f_flags & O_DIRECT && buffered) {
                         invalidate_mapping_pages(inode->i_mapping,
                               start_pos >> PAGE_CACHE_SHIFT,
                              (start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);