ext4: serialize dio nonlocked reads with defrag workers

Inode's block defrag and ext4_change_inode_journal_flag() may
affect nonlocked DIO reads result, so proper synchronization
required.

- Add missed inode_dio_wait() calls where appropriate
- Check inode state under extra i_dio_count reference.

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, 17 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index edb049579420..1be2b4472a83 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1358,6 +1358,8 @@ enum {
         EXT4_STATE_DIO_UNWRITTEN,       /* need convert on dio done*/
         EXT4_STATE_NEWENTRY,            /* File just added to dir */
         EXT4_STATE_DELALLOC_RESERVED,   /* blks already reserved for delalloc */
+        EXT4_STATE_DIOREAD_LOCK,        /* Disable support for dio read
+                                           nolocking */
 };
 
 #define EXT4_INODE_BIT_FNS(name, field, offset)                         \
@@ -2469,6 +2471,21 @@ static inline void set_bitmap_uptodate(struct buffer_head *bh)
         set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
 }
 
+/*
+ * Disable DIO read nolock optimization, so new dioreaders will be forced
+ * to grab i_mutex
+ */
+static inline void ext4_inode_block_unlocked_dio(struct inode *inode)
+{
+        ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
+        smp_mb();
+}
+static inline void ext4_inode_resume_unlocked_dio(struct inode *inode)
+{
+        smp_mb();
+        ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
+}
+
 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
 
 /* For ioend & aio unwritten conversion wait queues */