ext4: fix unwritten counter leakage

ext4_set_io_unwritten_flag() will increment i_unwritten counter, so
once we mark end_io with EXT4_END_IO_UNWRITTEN we have to revert it back
on error path.

 - add missed error checks to prevent counter leakage
 - ext4_end_io_nolock() will clear EXT4_END_IO_UNWRITTEN flag to signal
   that conversion finished.
 - add BUG_ON to ext4_free_end_io() to prevent similar leakage in future.

Visible effect of this bug is that unaligned aio_stress may deadlock

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 14 insertions, 7 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a1f56c3e773b..54a94426ef7b 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3633,6 +3633,8 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
         if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
                 ret = ext4_split_unwritten_extents(handle, inode, map,
                                                    path, flags);
+                if (ret <= 0)
+                        goto out;
                 /*
                  * Flag the inode(non aio case) or end_io struct (aio case)
                  * that this IO needs to conversion to written when IO is
@@ -3878,6 +3880,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
         struct ext4_allocation_request ar;
         ext4_io_end_t *io = ext4_inode_aio(inode);
         ext4_lblk_t cluster_offset;
+        int set_unwritten = 0;
 
         ext_debug("blocks %u/%u requested for inode %lu\n",
                   map->m_lblk, map->m_len, inode->i_ino);
@@ -4100,13 +4103,8 @@ got_allocated_blocks:
                  * For non asycn direct IO case, flag the inode state
                  * that we need to perform conversion when IO is done.
                  */
-                if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
-                        if (io)
-                                ext4_set_io_unwritten_flag(inode, io);
-                        else
-                                ext4_set_inode_state(inode,
-                                                     EXT4_STATE_DIO_UNWRITTEN);
-                }
+                if ((flags & EXT4_GET_BLOCKS_PRE_IO))
+                        set_unwritten = 1;
                 if (ext4_should_dioread_nolock(inode))
                         map->m_flags |= EXT4_MAP_UNINIT;
         }
@@ -4118,6 +4116,15 @@ got_allocated_blocks:
         if (!err)
                 err = ext4_ext_insert_extent(handle, inode, path,
                                              &newex, flags);
+
+        if (!err && set_unwritten) {
+                if (io)
+                        ext4_set_io_unwritten_flag(inode, io);
+                else
+                        ext4_set_inode_state(inode,
+                                             EXT4_STATE_DIO_UNWRITTEN);
+        }
+
         if (err && free_on_err) {
                 int fb_flags = flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE ?
                         EXT4_FREE_BLOCKS_NO_QUOT_UPDATE : 0;