f2fs: fix deadlock during inline_data conversion

A deadlock can be occurred:
Thread 1]                             Thread 2]
 - f2fs_write_data_pages              - f2fs_write_begin
   - lock_page(page #0)
                                        - grab_cache_page(page #X)
                                        - get_node_page(inode_page)
                                        - grab_cache_page(page #0)
                                          : to convert inline_data
   - f2fs_write_data_page
     - f2fs_write_inline_data
       - get_node_page(inode_page)

In this case, trying to lock inode_page and page #0 causes deadlock.
In order to avoid this, this patch adds a rule for this locking policy,
which is that page #0 should be locked followed by inode_page lock.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 12dd58aa569a6218d82be720dc73e847fec956e3..c7bc6264110349abba3471cbdbb6329303261d08 100644 (file)
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -936,6 +936,17 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
        trace_f2fs_write_begin(inode, pos, len, flags);
 
        f2fs_balance_fs(sbi);
+
+       /*
+        * We should check this at this moment to avoid deadlock on inode page
+        * and #0 page. The locking rule for inline_data conversion should be:
+        * lock_page(page #0) -> lock_page(inode_page)
+        */
+       if (index != 0) {
+               err = f2fs_convert_inline_inode(inode);
+               if (err)
+                       goto fail;
+       }
 repeat:
        page = grab_cache_page_write_begin(mapping, index, flags);
        if (!page) {
@@ -960,21 +971,10 @@ repeat:
                        set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
                        sync_inode_page(&dn);
                        goto put_next;
-               } else if (page->index == 0) {
-                       err = f2fs_convert_inline_page(&dn, page);
-                       if (err)
-                               goto put_fail;
-               } else {
-                       struct page *p = grab_cache_page(inode->i_mapping, 0);
-                       if (!p) {
-                               err = -ENOMEM;
-                               goto put_fail;
-                       }
-                       err = f2fs_convert_inline_page(&dn, p);
-                       f2fs_put_page(p, 1);
-                       if (err)
-                               goto put_fail;
                }
+               err = f2fs_convert_inline_page(&dn, page);
+               if (err)
+                       goto put_fail;
        }
        err = f2fs_reserve_block(&dn, index);
        if (err)