Re: [PATCH 01/26] cifs: Fix duplicate fscache cookie warnings

Jeff Layton
2024-04-15T11:25:33Z

On Thu, 2024-03-28 at 16:33 +0000, David Howells wrote:
> fscache emits a lot of duplicate cookie warnings with cifs because the
> index key for the fscache cookies does not include everything that the
> cifs_find_inode() function does. The latter is used with iget5_locked() to
> distinguish between inodes in the local inode cache.
>
> Fix this by adding the creation time and file type to the fscache cookie
> key.
>
> Additionally, add a couple of comments to note that if one is changed the
> other must be also.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Steve French <sfrench@samba.org>
> cc: Shyam Prasad N <nspmangalore@gmail.com>
> cc: Rohith Surabattula <rohiths.msft@gmail.com>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: linux-cifs@vger.kernel.org
> cc: netfs@lists.linux.dev
> cc: linux-fsdevel@vger.kernel.org
> ---
> fs/smb/client/fscache.c | 16 +++++++++++++++-
> fs/smb/client/inode.c | 2 ++
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/smb/client/fscache.c b/fs/smb/client/fscache.c
> index c4a3cb736881..340efce8f052 100644
> --- a/fs/smb/client/fscache.c
> +++ b/fs/smb/client/fscache.c
> @@ -12,6 +12,16 @@
> #include "cifs_fs_sb.h"
> #include "cifsproto.h"
>
> +/*
> + * Key for fscache inode. [!] Contents must match comparisons in cifs_find_inode().
> + */
> +struct cifs_fscache_inode_key {
> +
> + __le64 uniqueid; /* server inode number */
> + __le64 createtime; /* creation time on server */
> + u8 type; /* S_IFMT file type */
> +} __packed;
> +

Interesting. So the uniqueid of the inode is not unique within the fs?
Or are the clients are mounting shares that span multiple filesystems?
Or, are we looking at a situation where the uniqueid is being quickly
reused for new inodes after the original inode is unlinked?

Should we be mixing in a fsid (or whatever the windows equivalent is)?

> static void cifs_fscache_fill_volume_coherency(
> struct cifs_tcon *tcon,
> struct cifs_fscache_volume_coherency_data *cd)
> @@ -97,15 +107,19 @@ void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon)
> void cifs_fscache_get_inode_cookie(struct inode *inode)
> {
> struct cifs_fscache_inode_coherency_data cd;
> + struct cifs_fscache_inode_key key;
> struct cifsInodeInfo *cifsi = CIFS_I(inode);
> struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
> struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
>
> + key.uniqueid = cpu_to_le64(cifsi->uniqueid);
> + key.createtime = cpu_to_le64(cifsi->createtime);
> + key.type = (inode->i_mode & S_IFMT) >> 12;
> cifs_fscache_fill_coherency(&cifsi->netfs.inode, &cd);
>
> cifsi->netfs.cache =
> fscache_acquire_cookie(tcon->fscache, 0,
> - &cifsi->uniqueid, sizeof(cifsi->uniqueid),
> + &key, sizeof(key),
> &cd, sizeof(cd),
> i_size_read(&cifsi->netfs.inode));
> if (cifsi->netfs.cache)
> diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
> index d28ab0af6049..91b07ef9e25c 100644
> --- a/fs/smb/client/inode.c
> +++ b/fs/smb/client/inode.c
> @@ -1351,6 +1351,8 @@ cifs_find_inode(struct inode *inode, void *opaque)
> {
> struct cifs_fattr *fattr = opaque;
>
> + /* [!] The compared values must be the same in struct cifs_fscache_inode_key. */
> +
> /* don't match inode with different uniqueid */
> if (CIFS_I(inode)->uniqueid != fattr->cf_uniqueid)
> return 0;
>

Reviewed-by: Jeff Layton <jlayton@kernel.org>