linux-kernel - [PATCH 3/3] have pipefs ensure i_ino uniqueness by calling iunique and hashing the inode

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Message-Id: <200612291911.kBTJBLvx019107@dantu.rdu.redhat.com>
Date:	Fri, 29 Dec 2006 14:11:21 -0500
From:	Jeff Layton <jlayton@...hat.com>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] have pipefs ensure i_ino uniqueness by calling iunique and hashing the inode

This converts pipefs to use the new scheme. Here we're calling iunique to get
a unique i_ino value for the new inode, and then hashing it afterward. We
call iunique with a max_reserved value of 1 to avoid collision with the root
inode.  Since the inode is now hashed, we need to take care that we end up in
generic_delete_inode rather than generic_forget_inode or we'll create a nasty
leak, so we clear_nlink when we destroy the pipe info.

I'm not certain that this is the right place to add the clear_nlink, though
it does seem to work. I'm open to suggestions on a better place to put
this, or of a better way to make sure that we end up with i_nlink == 0 at
iput time.

Signed-off-by: Jeff Layton <jlayton@...hat.com>

diff --git a/fs/pipe.c b/fs/pipe.c
index 68090e8..1d44ff0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -825,6 +825,7 @@ void free_pipe_info(struct inode *inode)
 {
 	__free_pipe_info(inode->i_pipe);
 	inode->i_pipe = NULL;
+	clear_nlink(inode);
 }

 static struct vfsmount *pipe_mnt __read_mostly;
@@ -871,6 +872,8 @@ static struct inode * get_pipe_inode(void)
 	inode->i_uid = current->fsuid;
 	inode->i_gid = current->fsgid;
 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	inode->i_ino = iunique(pipe_mnt->mnt_sb, 1);
+	insert_inode_hash(inode);

 	return inode;

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