ext4: restart ext4_ext_remove_space() after transaction restart

If i_data_sem was internally dropped due to transaction restart, it is
necessary to restart path look-up because extents tree was possibly
modified by ext4_get_block().

https://bugzilla.kernel.org/show_bug.cgi?id=15827

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

1 files changed, 9 insertions, 7 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index ffcaa1137def..0a47becf668a 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -107,11 +107,8 @@ static int ext4_ext_truncate_extend_restart(handle_t *handle,
         if (err <= 0)
                 return err;
         err = ext4_truncate_restart_trans(handle, inode, needed);
-        /*
-         * We have dropped i_data_sem so someone might have cached again
-         * an extent we are going to truncate.
-         */
-        ext4_ext_invalidate_cache(inode);
+        if (err == 0)
+                err = -EAGAIN;
 
         return err;
 }
@@ -2359,7 +2356,7 @@ static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start)
         int depth = ext_depth(inode);
         struct ext4_ext_path *path;
         handle_t *handle;
-        int i = 0, err = 0;
+        int i, err;
 
         ext_debug("truncate since %u\n", start);
 
@@ -2368,23 +2365,26 @@ static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start)
         if (IS_ERR(handle))
                 return PTR_ERR(handle);
 
+again:
         ext4_ext_invalidate_cache(inode);
 
         /*
          * We start scanning from right side, freeing all the blocks
          * after i_size and walking into the tree depth-wise.
          */
+        depth = ext_depth(inode);
         path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_NOFS);
         if (path == NULL) {
                 ext4_journal_stop(handle);
                 return -ENOMEM;
         }
+        path[0].p_depth = depth;
         path[0].p_hdr = ext_inode_hdr(inode);
         if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
                 err = -EIO;
                 goto out;
         }
-        path[0].p_depth = depth;
+        i = err = 0;
 
         while (i >= 0 && err == 0) {
                 if (i == depth) {
@@ -2478,6 +2478,8 @@ static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start)
 out:
         ext4_ext_drop_refs(path);
         kfree(path);
+        if (err == -EAGAIN)
+                goto again;
         ext4_journal_stop(handle);
 
         return err;