From: Matthew Wilcox <willy@infradead.org>
To: jiangyiwen <jiangyiwen@huawei.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>,
Latchesar Ionkov <lucho@ionkov.net>,
Eric Van Hensbergen <ericvh@gmail.com>,
linux-kernel@vger.kernel.org, Ron Minnich <rminnich@sandia.gov>,
linux-fsdevel@vger.kernel.org,
v9fs-developer@lists.sourceforge.net
Subject: Re: [V9fs-developer] [PATCH v2 3/6] 9p: Replace the fidlist with an IDR
Date: Thu, 12 Jul 2018 19:48:03 -0700 [thread overview]
Message-ID: <20180713024803.GA2860@bombadil.infradead.org> (raw)
In-Reply-To: <5B4808FE.7010500@huawei.com>
On Fri, Jul 13, 2018 at 10:05:50AM +0800, jiangyiwen wrote:
> > @@ -908,30 +908,29 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
> > {
> > int ret;
> > struct p9_fid *fid;
> > - unsigned long flags;
> >
> > p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
> > fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
> > if (!fid)
> > return NULL;
> >
> > - ret = p9_idpool_get(clnt->fidpool);
> > - if (ret < 0)
> > - goto error;
> > - fid->fid = ret;
> > -
> > memset(&fid->qid, 0, sizeof(struct p9_qid));
> > fid->mode = -1;
> > fid->uid = current_fsuid();
> > fid->clnt = clnt;
> > fid->rdir = NULL;
> > - spin_lock_irqsave(&clnt->lock, flags);
> > - list_add(&fid->flist, &clnt->fidlist);
> > - spin_unlock_irqrestore(&clnt->lock, flags);
> > + fid->fid = 0;
> >
> > - return fid;
> > + idr_preload(GFP_KERNEL);
>
> It is best to use GFP_NOFS instead, or else it may cause some
> unpredictable problem, because when out of memory it will
> reclaim memory from v9fs.
Earlier in this function, fid was allocated with GFP_KERNEL:
> > fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
> > + spin_lock_irq(&clnt->lock);
> > + ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
> > + GFP_NOWAIT);
> > + spin_unlock_irq(&clnt->lock);
>
> use spin_lock instead, clnt->lock is not used in irq context.
I don't think that's right. What about p9_fid_destroy? It was already
using spin_lock_irqsave(), so I just assumed that whoever wrote that
code at least considered that it might be called from interrupt context.
Also consider p9_free_req() which shares the same lock. We could get
rid of clnt->lock altogether as there's a lock embedded in each IDR,
but that'll introduce an unwanted dependence on the RDMA tree in this
merge window.
> > @@ -1095,14 +1086,11 @@ void p9_client_destroy(struct p9_client *clnt)
> >
> > v9fs_put_trans(clnt->trans_mod);
> >
> > - list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist) {
> > + idr_for_each_entry(&clnt->fids, fid, id) {
> > pr_info("Found fid %d not clunked\n", fid->fid);
> > p9_fid_destroy(fid);
> > }
> >
> > - if (clnt->fidpool)
> > - p9_idpool_destroy(clnt->fidpool);
> > -
>
> I suggest add idr_destroy in the end.
Why? p9_fid_destroy calls idr_remove() for each fid, so it'll already
be empty.
Thanks for all the review, to everyone who's submitted review. This is
a really healthy community.
next prev parent reply other threads:[~2018-07-13 2:48 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-11 21:02 [PATCH v2 0/6] 9p: Use IDRs more effectively Matthew Wilcox
2018-07-11 21:02 ` [PATCH v2 1/6] 9p: Fix comment on smp_wmb Matthew Wilcox
2018-07-12 11:55 ` [V9fs-developer] " Greg Kurz
2018-07-11 21:02 ` [PATCH v2 2/6] 9p: Change p9_fid_create calling convention Matthew Wilcox
2018-07-12 2:15 ` [V9fs-developer] " piaojun
2018-07-12 11:56 ` Greg Kurz
2018-07-13 1:18 ` jiangyiwen
2018-07-11 21:02 ` [PATCH v2 3/6] 9p: Replace the fidlist with an IDR Matthew Wilcox
2018-07-12 11:17 ` Dominique Martinet
2018-07-12 11:23 ` Matthew Wilcox
2018-07-12 11:30 ` Dominique Martinet
2018-07-13 2:05 ` [V9fs-developer] " jiangyiwen
2018-07-13 2:48 ` Matthew Wilcox [this message]
2018-07-11 21:02 ` [PATCH v2 4/6] 9p: Embed wait_queue_head into p9_req_t Matthew Wilcox
2018-07-12 14:36 ` [V9fs-developer] " Greg Kurz
2018-07-12 14:40 ` Dominique Martinet
2018-07-12 14:59 ` Greg Kurz
2018-07-11 21:02 ` [PATCH v2 5/6] 9p: Use a slab for allocating requests Matthew Wilcox
2018-07-18 10:05 ` Dominique Martinet
2018-07-18 11:49 ` Matthew Wilcox
2018-07-18 12:46 ` Dominique Martinet
2018-07-23 11:52 ` Greg Kurz
2018-07-23 12:25 ` Dominique Martinet
2018-07-23 14:24 ` Greg Kurz
2018-07-30 9:31 ` Dominique Martinet
2018-07-30 9:34 ` [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs Dominique Martinet
2018-07-30 9:34 ` [PATCH 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-07-31 1:18 ` [V9fs-developer] " piaojun
2018-07-31 1:35 ` Dominique Martinet
2018-07-31 1:45 ` piaojun
2018-07-31 2:46 ` Matthew Wilcox
2018-07-31 4:17 ` Dominique Martinet
2018-08-01 14:28 ` [V9fs-developer] " Greg Kurz
2018-08-01 15:22 ` Dominique Martinet
2018-07-31 0:55 ` [V9fs-developer] [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs piaojun
2018-07-31 1:12 ` Dominique Martinet
2018-07-31 1:28 ` piaojun
2018-08-01 14:14 ` Greg Kurz
2018-08-01 14:38 ` Dominique Martinet
2018-08-01 15:03 ` Greg Kurz
2018-08-02 2:37 ` [PATCH v2 " Dominique Martinet
2018-08-02 2:37 ` [PATCH v2 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-08-02 4:58 ` [V9fs-developer] " Dominique Martinet
2018-08-02 9:23 ` [PATCH v2 1/2] net/9p: embed fcall in req to round down buffer allocs Greg Kurz
2018-08-02 22:03 ` Dominique Martinet
2018-08-09 14:33 ` [PATCH v3 " Dominique Martinet
2018-08-09 14:33 ` [PATCH v3 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-08-10 1:23 ` piaojun
2018-08-10 1:41 ` Dominique Martinet
2018-08-10 1:49 ` piaojun
2018-08-10 0:47 ` [PATCH v3 1/2] net/9p: embed fcall in req to round down buffer allocs piaojun
2018-07-11 21:02 ` [PATCH v2 6/6] 9p: Remove p9_idpool Matthew Wilcox
2018-07-11 23:37 ` [PATCH v2 0/6] 9p: Use IDRs more effectively Dominique Martinet
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