Btrfs: when forced to cow for file_write, get the page uptodate first

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

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a3183972f310..b93d790e7484 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1268,6 +1268,8 @@ static int prepare_pages(struct btrfs_trans_handle *trans,
                          struct page **pages,
                          size_t num_pages,
                          loff_t pos,
+                         unsigned long first_index,
+                         unsigned long last_index,
                          size_t write_bytes)
 {
         int i;
@@ -1289,6 +1291,13 @@ static int prepare_pages(struct btrfs_trans_handle *trans,
                 }
                 offset = pos & (PAGE_CACHE_SIZE -1);
                 this_write = min(PAGE_CACHE_SIZE - offset, write_bytes);
+                if (!PageUptodate(pages[i]) &&
+                   (pages[i]->index == first_index ||
+                    pages[i]->index == last_index) && pos < isize) {
+                        ret = mpage_readpage(pages[i], btrfs_get_block);
+                        BUG_ON(ret);
+                        lock_page(pages[i]);
+                }
                 ret = nobh_prepare_write(pages[i], offset,
                                          offset + this_write,
                                          btrfs_get_block);
@@ -1323,6 +1332,8 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         struct inode *inode = file->f_path.dentry->d_inode;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct page *pages[1];
+        unsigned long first_index;
+        unsigned long last_index;
 
         if (file->f_flags & O_DIRECT)
                 return -EINVAL;
@@ -1340,13 +1351,15 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 goto out;
         file_update_time(file);
         mutex_lock(&inode->i_mutex);
+        first_index = pos >> PAGE_CACHE_SHIFT;
+        last_index = (pos + count) >> PAGE_CACHE_SHIFT;
         while(count > 0) {
                 size_t offset = pos & (PAGE_CACHE_SIZE - 1);
                 size_t write_bytes = min(count, PAGE_CACHE_SIZE - offset);
                 size_t num_pages = (write_bytes + PAGE_CACHE_SIZE - 1) >>
                                         PAGE_CACHE_SHIFT;
                 ret = prepare_pages(NULL, root, file, pages, num_pages,
-                                    pos, write_bytes);
+                                    pos, first_index, last_index, write_bytes);
                 BUG_ON(ret);
                 ret = btrfs_copy_from_user(pos, num_pages,
                                            write_bytes, pages, buf);