Ensure we have lower inodes in prepare/commit_write.
Signed-off-by: Erez Zadok <ezk@xxxxxxxxxxxxx>
---
fs/unionfs/mmap.c | 26 +++++++++++++++++++++-----
1 files changed, 21 insertions(+), 5 deletions(-)
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
index a0e654b..ad770ac 100644
--- a/fs/unionfs/mmap.c
+++ b/fs/unionfs/mmap.c
@@ -224,13 +224,26 @@ out:
static int unionfs_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
+ int err;
+
+ unionfs_read_lock(file->f_path.dentry->d_sb, UNIONFS_SMUTEX_PARENT);
/*
- * Just copy lower inode attributes and return success. Not much
- * else to do here. No need to lock either (lockdep won't like it).
- * Let commit_write do all the hard work instead.
+ * This is the only place where we unconditionally copy the lower
+ * attribute times before calling unionfs_file_revalidate. The
+ * reason is that our ->write calls do_sync_write which in turn will
+ * call our ->prepare_write and then ->commit_write. Before our
+ * ->write is called, the lower mtimes are in sync, but by the time
+ * the VFS calls our ->commit_write, the lower mtimes have changed.
+ * Therefore, the only reasonable time for us to sync up from the
+ * changed lower mtimes, and avoid an invariant violation warning,
+ * is here, in ->prepare_write.
*/
unionfs_copy_attr_times(file->f_path.dentry->d_inode);
- return 0;
+ err = unionfs_file_revalidate(file, true);
+ unionfs_check_file(file);
+ unionfs_read_unlock(file->f_path.dentry->d_sb);
+
+ return err;
}
static int unionfs_commit_write(struct file *file, struct page *page,
@@ -252,7 +265,6 @@ static int unionfs_commit_write(struct file *file, struct page *page,
unionfs_check_file(file);
inode = page->mapping->host;
- lower_inode = unionfs_lower_inode(inode);
if (UNIONFS_F(file) != NULL)
lower_file = unionfs_lower_file(file);
@@ -282,6 +294,10 @@ static int unionfs_commit_write(struct file *file, struct page *page,
goto out;
/* if vfs_write succeeded above, sync up our times/sizes */
+ lower_inode = lower_file->f_path.dentry->d_inode;
+ if (!lower_inode)
+ lower_inode = unionfs_lower_inode(inode);
+ BUG_ON(!lower_inode);
fsstack_copy_inode_size(inode, lower_inode);
unionfs_copy_attr_times(inode);
mark_inode_dirty_sync(inode);
--
1.5.2.2
-
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