Re: [PATCH v2] cifs: remove unnecessary copies of tcon->crfid.fid

[Aurélien Aptel]

Hi,

This is better I think.

Muhammad Usama Anjum <musamaanjum@xxxxxxxxx> writes:
> @@ -894,6 +891,10 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
>  
>  	/* BB TBD check to see if oplock level check can be removed below */
>  	if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE) {
> +		/*
> +		 * caller expects this func to set the fid in crfid to valid
> +		 * cached root, so increment the refcount.
> +		 */

This comment is misleading. crfid variable doesn't exist anymore, and
the kref_get() here is because of this commit:

    commit 2f94a3125b87
    Author: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
    Date:   Thu Mar 28 11:20:02 2019 +1000
    
        cifs: fix kref underflow in close_shroot()

        [...]
-->     This extra get() is only used to hold the structure until we get a lease
-->     break from the server at which point we will kref_put() it during lease
-->     processing.
        [...]



When we queue a lease break, we usually get() the cifsFileInfo, but if
that cifsFileInfo is backed by a cached_fid, the cached_fid isn't
bumped. That commit was probably a work around for that.

@Ronnie :

struct cached_fid is starting to look very much like struct
cifsFileInfo. I wonder why we couldn't use it, along with
find_writable_file()/find_readable_file() to handle the caching.

Alternatively, make cifsFileInfo use cached_fid (perhaps renaming it in
the process, I don't know)

Because I suspect a lot more issues will come up regarding cached_fid
refcount and cifsFileInfo refcount going out of sync otherwise.

Cheers,
-- 
Aurélien Aptel / SUSE Labs Samba Team
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