Re: [PATCH 2/2] gfs2: replace usage of found with dedicated list iterator variable

From: Andreas Gruenbacher
Date: Mon Apr 04 2022 - 10:45:37 EST


Jakob,

On Fri, Apr 1, 2022 at 12:40 AM Jakob Koschel <jakobkoschel@xxxxxxxxx> 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@xxxxxxxxxxxxxx/ [1]
> Signed-off-by: Jakob Koschel <jakobkoschel@xxxxxxxxx>
> ---
> fs/gfs2/quota.c | 13 ++++++-------
> fs/gfs2/recovery.c | 22 ++++++++++------------
> 2 files changed, 16 insertions(+), 19 deletions(-)
>
> diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
> index be0997e24d60..dafd04fb9164 100644
> --- a/fs/gfs2/quota.c
> +++ b/fs/gfs2/quota.c
> @@ -443,7 +443,7 @@ static int qd_check_sync(struct gfs2_sbd *sdp, struct gfs2_quota_data *qd,
>
> static int qd_fish(struct gfs2_sbd *sdp, struct gfs2_quota_data **qdp)
> {
> - struct gfs2_quota_data *qd = NULL;
> + struct gfs2_quota_data *qd = NULL, *iter;
> int error;
> int found = 0;
>
> @@ -454,15 +454,14 @@ static int qd_fish(struct gfs2_sbd *sdp, struct gfs2_quota_data **qdp)
>
> spin_lock(&qd_lock);
>
> - list_for_each_entry(qd, &sdp->sd_quota_list, qd_list) {
> - found = qd_check_sync(sdp, qd, &sdp->sd_quota_sync_gen);
> - if (found)
> + list_for_each_entry(iter, &sdp->sd_quota_list, qd_list) {
> + found = qd_check_sync(sdp, iter, &sdp->sd_quota_sync_gen);
> + if (found) {
> + qd = iter;

we might as well get rid of 'found' here like in the below two
changes. Let me fix that up.

> break;
> + }
> }
>
> - if (!found)
> - qd = NULL;
> -
> spin_unlock(&qd_lock);
>
> if (qd) {
> diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c
> index 016ed1b2ca1d..2bb085a72e8e 100644
> --- a/fs/gfs2/recovery.c
> +++ b/fs/gfs2/recovery.c
> @@ -55,17 +55,16 @@ int gfs2_replay_read_block(struct gfs2_jdesc *jd, unsigned int blk,
> int gfs2_revoke_add(struct gfs2_jdesc *jd, u64 blkno, unsigned int where)
> {
> struct list_head *head = &jd->jd_revoke_list;
> - struct gfs2_revoke_replay *rr;
> - int found = 0;
> + struct gfs2_revoke_replay *rr = NULL, *iter;
>
> - list_for_each_entry(rr, head, rr_list) {
> - if (rr->rr_blkno == blkno) {
> - found = 1;
> + list_for_each_entry(iter, head, rr_list) {
> + if (iter->rr_blkno == blkno) {
> + rr = iter;
> break;
> }
> }
>
> - if (found) {
> + if (rr) {
> rr->rr_where = where;
> return 0;
> }
> @@ -83,18 +82,17 @@ int gfs2_revoke_add(struct gfs2_jdesc *jd, u64 blkno, unsigned int where)
>
> int gfs2_revoke_check(struct gfs2_jdesc *jd, u64 blkno, unsigned int where)
> {
> - struct gfs2_revoke_replay *rr;
> + struct gfs2_revoke_replay *rr = NULL, *iter;
> int wrap, a, b, revoke;
> - int found = 0;
>
> - list_for_each_entry(rr, &jd->jd_revoke_list, rr_list) {
> - if (rr->rr_blkno == blkno) {
> - found = 1;
> + list_for_each_entry(iter, &jd->jd_revoke_list, rr_list) {
> + if (iter->rr_blkno == blkno) {
> + rr = iter;
> break;
> }
> }
>
> - if (!found)
> + if (!rr)
> return 0;
>
> wrap = (rr->rr_where < jd->jd_replay_tail);
> --
> 2.25.1
>

Thanks,
Andreas