commit 76894f3e2f71177747b8b4763fb180e800279585
author Paulo Alcantara <pc@cjr.nz> Mon Oct 03 18:43:50 2022 -0300
committer Steve French <stfrench@microsoft.com> Thu Oct 13 09:36:04 2022 -0500
tree d0382d6389d324b5d7421ee960a60af74415b631
parent 977bb6530807a9a8e7f29d7dfba5737135b50df6

cifs: improve symlink handling for smb2+

When creating inode for symlink, the client used to send below
requests to fill it in:

    * create+query_info+close (STATUS_STOPPED_ON_SYMLINK)
    * create(+reparse_flag)+query_info+close (set file attrs)
    * create+ioctl(get_reparse)+close (query reparse tag)

and then for every access to the symlink dentry, the ->link() method
would send another:

    * create+ioctl(get_reparse)+close (parse symlink)

So, in order to improve:

    (i) Get rid of unnecessary roundtrips and then resolve symlinks as
	follows:

        * create+query_info+close (STATUS_STOPPED_ON_SYMLINK +
	                           parse symlink + get reparse tag)
        * create(+reparse_flag)+query_info+close (set file attrs)

    (ii) Set the resolved symlink target directly in inode->i_link and
         use simple_get_link() for ->link() to simply return it.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.c

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 8042d72..c6ac192 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -396,6 +396,7 @@ cifs_alloc_inode(struct super_block *sb)
 	cifs_inode->epoch = 0;
 	spin_lock_init(&cifs_inode->open_file_lock);
 	generate_random_uuid(cifs_inode->lease_key);
+	cifs_inode->symlink_target = NULL;
 
 	/*
 	 * Can not set i_flags here - they get immediately overwritten to zero
@@ -412,7 +413,11 @@ cifs_alloc_inode(struct super_block *sb)
 static void
 cifs_free_inode(struct inode *inode)
 {
-	kmem_cache_free(cifs_inode_cachep, CIFS_I(inode));
+	struct cifsInodeInfo *cinode = CIFS_I(inode);
+
+	if (S_ISLNK(inode->i_mode))
+		kfree(cinode->symlink_target);
+	kmem_cache_free(cifs_inode_cachep, cinode);
 }
 
 static void
@@ -1139,7 +1144,7 @@ const struct inode_operations cifs_file_inode_ops = {
 };
 
 const struct inode_operations cifs_symlink_inode_ops = {
-	.get_link = cifs_get_link,
+	.get_link = simple_get_link,
 	.permission = cifs_permission,
 	.listxattr = cifs_listxattr,
 };