[PATCH 3.4 046/172] debugfs: leave freeing a symlink body until inode eviction

lizf
2015-06-16T08:43:16Z

From: Al Viro <viro@zeniv.linux.org.uk>

3.4.108-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit 0db59e59299f0b67450c5db21f7f316c8fb04e84 upstream.

As it is, we have debugfs_remove() racing with symlink traversals.
Supply ->evict_inode() and do freeing there - inode will remain
pinned until we are done with the symlink body.

And rip the idiocy with checking if dentry is positive right after
we'd verified debugfs_positive(), which is a stronger check...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[lizf: Backported to 3.4:
- call end_writeback() instead of clear_inode()
- call truncate_inode_pages() instead of truncate_inode_pages_final()]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
fs/debugfs/inode.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 47d64e9..7b65755 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -238,10 +238,19 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root)
return 0;
}

+static void debugfs_evict_inode(struct inode *inode)
+{
+ truncate_inode_pages(&inode->i_data, 0);
+ end_writeback(inode);
+ if (S_ISLNK(inode->i_mode))
+ kfree(inode->i_private);
+}
+
static const struct super_operations debugfs_super_operations = {
.statfs = simple_statfs,
.remount_fs = debugfs_remount,
.show_options = debugfs_show_options,
+ .evict_inode = debugfs_evict_inode,
};

static int debug_fill_super(struct super_block *sb, void *data, int silent)
@@ -459,23 +468,14 @@ static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
int ret = 0;

if (debugfs_positive(dentry)) {
- if (dentry->d_inode) {
- dget(dentry);
- switch (dentry->d_inode->i_mode & S_IFMT) {
- case S_IFDIR:
- ret = simple_rmdir(parent->d_inode, dentry);
- break;
- case S_IFLNK:
- kfree(dentry->d_inode->i_private);
- /* fall through */
- default:
- simple_unlink(parent->d_inode, dentry);
- break;
- }
- if (!ret)
- d_delete(dentry);
- dput(dentry);
- }
+ dget(dentry);
+ if (S_ISDIR(dentry->d_inode->i_mode))
+ ret = simple_rmdir(parent->d_inode, dentry);
+ else
+ simple_unlink(parent->d_inode, dentry);
+ if (!ret)
+ d_delete(dentry);
+ dput(dentry);
}
return ret;
}
--
1.9.1