linux-kernel - Re: [PATCH 2/2] ceph: replace usage of found with dedicated list iterator variable

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Message-ID: <fc02b2d29ecb7e277d48afb340b01cdc684e2e5a.camel@kernel.org>
Date:   Fri, 01 Apr 2022 11:23:52 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Jakob Koschel <jakobkoschel@...il.com>
Cc:     Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH 2/2] ceph: replace usage of found with dedicated list
 iterator variable

On Thu, 2022-03-31 at 23:53 +0200, Jakob Koschel wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
> 
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate iterator variable instead of a
> found boolean [1].
> 
> This removes the need to use a found variable and simply checking if
> the variable was set, can determine if the break/goto was hit.
> 
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
> ---
>  fs/ceph/caps.c | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index 519750bc5a1a..70f9c5ffa9b7 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -3179,10 +3179,9 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
>  				struct ceph_snap_context *snapc)
>  {
>  	struct inode *inode = &ci->vfs_inode;
> -	struct ceph_cap_snap *capsnap = NULL;
> +	struct ceph_cap_snap *capsnap = NULL, *iter;
>  	int put = 0;
>  	bool last = false;
> -	bool found = false;
>  	bool flush_snaps = false;
>  	bool complete_capsnap = false;
>  
> @@ -3209,14 +3208,14 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
>  		     ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
>  		     last ? " LAST" : "");
>  	} else {
> -		list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
> -			if (capsnap->context == snapc) {
> -				found = true;
> +		list_for_each_entry(iter, &ci->i_cap_snaps, ci_item) {
> +			if (iter->context == snapc) {
> +				capsnap = iter;
>  				break;
>  			}
>  		}
>  
> -		if (!found) {
> +		if (!capsnap) {
>  			/*
>  			 * The capsnap should already be removed when removing
>  			 * auth cap in the case of a forced unmount.
> @@ -3766,8 +3765,7 @@ static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,
>  	struct ceph_inode_info *ci = ceph_inode(inode);
>  	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
>  	u64 follows = le64_to_cpu(m->snap_follows);
> -	struct ceph_cap_snap *capsnap;
> -	bool flushed = false;
> +	struct ceph_cap_snap *capsnap = NULL, *iter;
>  	bool wake_ci = false;
>  	bool wake_mdsc = false;
>  
> @@ -3775,26 +3773,26 @@ static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,
>  	     inode, ci, session->s_mds, follows);
>  
>  	spin_lock(&ci->i_ceph_lock);
> -	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
> -		if (capsnap->follows == follows) {
> -			if (capsnap->cap_flush.tid != flush_tid) {
> +	list_for_each_entry(iter, &ci->i_cap_snaps, ci_item) {
> +		if (iter->follows == follows) {
> +			if (iter->cap_flush.tid != flush_tid) {
>  				dout(" cap_snap %p follows %lld tid %lld !="
> -				     " %lld\n", capsnap, follows,
> -				     flush_tid, capsnap->cap_flush.tid);
> +				     " %lld\n", iter, follows,
> +				     flush_tid, iter->cap_flush.tid);
>  				break;
>  			}
> -			flushed = true;
> +			capsnap = iter;
>  			break;
>  		} else {
>  			dout(" skipping cap_snap %p follows %lld\n",
> -			     capsnap, capsnap->follows);
> +			     iter, iter->follows);
>  		}
>  	}
> -	if (flushed)
> +	if (capsnap)
>  		ceph_remove_capsnap(inode, capsnap, &wake_ci, &wake_mdsc);
>  	spin_unlock(&ci->i_ceph_lock);
>  
> -	if (flushed) {
> +	if (capsnap) {
>  		ceph_put_snap_context(capsnap->context);
>  		ceph_put_cap_snap(capsnap);
>  		if (wake_ci)

Thanks Jakob,

Both patches look fine. Applied to the ceph-client/testing branch. This
should make v5.19 if there are no issues.

Thanks!
-- 
Jeff Layton <jlayton@...nel.org>