Btrfs: O_DIRECT writes via buffered writes + invaldiate

This reworks the btrfs O_DIRECT write code a bit.  It had always fallen
back to buffered IO and done an invalidate, but needed to be updated
for the data=ordered code.  The invalidate wasn't actually removing pages
because they were still inside an ordered extent.

This also combines the O_DIRECT/O_SYNC paths where possible, and kicks
off IO in the main btrfs_file_write loop to keep the pipe down the the
disk full as we process long writes.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

3 files changed, 38 insertions, 31 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 3088a1184483..a03d1bbb19ad 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -905,6 +905,10 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         struct page *pinned[2];
         unsigned long first_index;
         unsigned long last_index;
+        int will_write;
+
+        will_write = ((file->f_flags & O_SYNC) || IS_SYNC(inode) ||
+                      (file->f_flags & O_DIRECT));
 
         nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
                      PAGE_CACHE_SIZE / (sizeof(struct page *)));
@@ -1001,15 +1005,24 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 if (ret)
                         goto out;
 
+                if (will_write) {
+                        btrfs_fdatawrite_range(inode->i_mapping, pos,
+                                               pos + write_bytes - 1,
+                                               WB_SYNC_NONE);
+                } else {
+                        balance_dirty_pages_ratelimited_nr(inode->i_mapping,
+                                                           num_pages);
+                        if (num_pages <
+                            (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
+                                btrfs_btree_balance_dirty(root, 1);
+                        btrfs_throttle(root);
+                }
+
                 buf += write_bytes;
                 count -= write_bytes;
                 pos += write_bytes;
                 num_written += write_bytes;
 
-                balance_dirty_pages_ratelimited_nr(inode->i_mapping, num_pages);
-                if (num_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
-                        btrfs_btree_balance_dirty(root, 1);
-                btrfs_throttle(root);
                 cond_resched();
         }
 out:
@@ -1023,36 +1036,29 @@ out_nolock:
                 page_cache_release(pinned[1]);
         *ppos = pos;
 
-        if (num_written > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
+        if (num_written > 0 && will_write) {
                 struct btrfs_trans_handle *trans;
 
-                err = btrfs_fdatawrite_range(inode->i_mapping, start_pos,
-                                             start_pos + num_written -1,
-                                             WB_SYNC_NONE);
-                if (err < 0)
-                        num_written = err;
-
-                err = btrfs_wait_on_page_writeback_range(inode->i_mapping,
-                                 start_pos, start_pos + num_written - 1);
-                if (err < 0)
+                err = btrfs_wait_ordered_range(inode, start_pos, num_written);
+                if (err)
                         num_written = err;
 
-                trans = btrfs_start_transaction(root, 1);
-                ret = btrfs_log_dentry_safe(trans, root, file->f_dentry);
-                if (ret == 0) {
-                        btrfs_sync_log(trans, root);
-                        btrfs_end_transaction(trans, root);
-                } else {
-                        btrfs_commit_transaction(trans, root);
+                if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
+                        trans = btrfs_start_transaction(root, 1);
+                        ret = btrfs_log_dentry_safe(trans, root,
+                                                    file->f_dentry);
+                        if (ret == 0) {
+                                btrfs_sync_log(trans, root);
+                                btrfs_end_transaction(trans, root);
+                        } else {
+                                btrfs_commit_transaction(trans, root);
+                        }
+                }
+                if (file->f_flags & O_DIRECT) {
+                        invalidate_mapping_pages(inode->i_mapping,
+                              start_pos >> PAGE_CACHE_SHIFT,
+                             (start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);
                 }
-        } else if (num_written > 0 && (file->f_flags & O_DIRECT)) {
-                do_sync_mapping_range(inode->i_mapping, start_pos,
-                                      start_pos + num_written - 1,
-                                      SYNC_FILE_RANGE_WRITE |
-                                      SYNC_FILE_RANGE_WAIT_AFTER);
-                invalidate_mapping_pages(inode->i_mapping,
-                      start_pos >> PAGE_CACHE_SHIFT,
-                     (start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);
         }
         current->backing_dev_info = NULL;
         return num_written ? num_written : err;
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index dcc1730dd837..2eb6caba57c2 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -397,7 +397,7 @@ void btrfs_start_ordered_extent(struct inode *inode,
 /*
  * Used to wait on ordered extents across a large range of bytes.
  */
-void btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
+int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 {
         u64 end;
         u64 orig_end;
@@ -451,6 +451,7 @@ again:
                        (unsigned long long)orig_end);
                 goto again;
         }
+        return 0;
 }
 
 /*
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index fd45519f30a8..f50f8870a144 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -135,7 +135,7 @@ struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
                                                          u64 file_offset);
 void btrfs_start_ordered_extent(struct inode *inode,
                                 struct btrfs_ordered_extent *entry, int wait);
-void btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len);
+int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len);
 struct btrfs_ordered_extent *
 btrfs_lookup_first_ordered_extent(struct inode * inode, u64 file_offset);
 int btrfs_ordered_update_i_size(struct inode *inode,