ext4: move ext4_update_i_disksize() into mpage_map_and_submit_extent()

The function ext4_update_i_disksize() is used in only one place, in
the function mpage_map_and_submit_extent().  Move its code to simplify
the code paths, and also move the call to ext4_mark_inode_dirty() into
the i_data_sem's critical region, to be consistent with all of the
other places where we update i_disksize.  That way, we also keep the
raw_inode's i_disksize protected, to avoid the following race:

      CPU #1                                 CPU #2

   down_write(&i_data_sem)
   Modify i_disk_size
   up_write(&i_data_sem)
                                        down_write(&i_data_sem)
                                        Modify i_disk_size
                                        Copy i_disk_size to on-disk inode
                                        up_write(&i_data_sem)
   Copy i_disk_size to on-disk inode

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f1c65dc..66946aa 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2466,23 +2466,6 @@ static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
        up_write(&EXT4_I(inode)->i_data_sem);
 }
 
-/*
- * Update i_disksize after writeback has been started. Races with truncate
- * are avoided by checking i_size under i_data_sem.
- */
-static inline void ext4_wb_update_i_disksize(struct inode *inode, loff_t newsize)
-{
-       loff_t i_size;
-
-       down_write(&EXT4_I(inode)->i_data_sem);
-       i_size = i_size_read(inode);
-       if (newsize > i_size)
-               newsize = i_size;
-       if (newsize > EXT4_I(inode)->i_disksize)
-               EXT4_I(inode)->i_disksize = newsize;
-       up_write(&EXT4_I(inode)->i_data_sem);
-}
-
 struct ext4_group_info {
        unsigned long   bb_state;
        struct rb_root  bb_free_root;

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7b93df9..f023f0c 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2247,13 +2247,23 @@ static int mpage_map_and_submit_extent(handle_t *handle,
                        return err;
        } while (map->m_len);
 
-       /* Update on-disk size after IO is submitted */
+       /*
+        * Update on-disk size after IO is submitted.  Races with
+        * truncate are avoided by checking i_size under i_data_sem.
+        */
        disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT;
        if (disksize > EXT4_I(inode)->i_disksize) {
                int err2;
-
-               ext4_wb_update_i_disksize(inode, disksize);
+               loff_t i_size;
+
+               down_write(&EXT4_I(inode)->i_data_sem);
+               i_size = i_size_read(inode);
+               if (disksize > i_size)
+                       disksize = i_size;
+               if (disksize > EXT4_I(inode)->i_disksize)
+                       EXT4_I(inode)->i_disksize = disksize;
                err2 = ext4_mark_inode_dirty(handle, inode);
+               up_write(&EXT4_I(inode)->i_data_sem);
                if (err2)
                        ext4_error(inode->i_sb,
                                   "Failed to mark inode %lu dirty",