linux-kernel - Re: [PATCH] ceph: match wait_for_completion

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Date:	Wed, 11 Mar 2015 20:42:23 +0800
From:	"Yan, Zheng" <ukernel@...il.com>
To:	Nicholas Mc Guire <der.herr@...r.at>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>, Yan Zheng <zyan@...hat.com>,
	Sage Weil <sage@...hat.com>,
	ceph-devel <ceph-devel@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ceph: match wait_for_completion_timeout return type

On Wed, Mar 11, 2015 at 7:04 PM, Nicholas Mc Guire <der.herr@...r.at> wrote:
> On Wed, 11 Mar 2015, Yan, Zheng wrote:
>
>> On Tue, Mar 10, 2015 at 11:18 PM, Nicholas Mc Guire <hofrat@...dl.org> wrote:
>> > return type of wait_for_completion_timeout is unsigned long not int. An
>> > appropriately named unsigned long is added and the assignment fixed up.
>> >
>> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
>> > ---
>> >
>> > This was only compile tested for x86_64_defconfig + CONFIG_CEPH_FS=m
>> >
>> > Patch is against 4.0-rc2 linux-next (localversion-next is -next-20150306)
>> >
>> >  fs/ceph/dir.c |    7 ++++---
>> >  1 file changed, 4 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
>> > index 83e9976..4bee6b7 100644
>> > --- a/fs/ceph/dir.c
>> > +++ b/fs/ceph/dir.c
>> > @@ -1218,6 +1218,7 @@ static int ceph_dir_fsync(struct file *file, loff_t start, loff_t end,
>> >         struct ceph_mds_request *req;
>> >         u64 last_tid;
>> >         int ret = 0;
>> > +       unsigned long time_left;
>> >
>> >         dout("dir_fsync %p\n", inode);
>> >         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
>> > @@ -1240,11 +1241,11 @@ static int ceph_dir_fsync(struct file *file, loff_t start, loff_t end,
>> >                 dout("dir_fsync %p wait on tid %llu (until %llu)\n",
>> >                      inode, req->r_tid, last_tid);
>> >                 if (req->r_timeout) {
>> > -                       ret = wait_for_completion_timeout(
>> > +                       time_left = wait_for_completion_timeout(
>> >                                 &req->r_safe_completion, req->r_timeout);
>> > -                       if (ret > 0)
>> > +                       if (time_left > 0)
>> >                                 ret = 0;
>> > -                       else if (ret == 0)
>> > +                       else if (!time_left)
>> >                                 ret = -EIO;  /* timed out */
>> >                 } else {
>> >                         wait_for_completion(&req->r_safe_completion);
>>
>> There are lots of similar codes in kernel. I don't think this code
>> causes problem in reality
>>
> true - there are 38 (of the initial 81 files) left for which no patch has been
> submitted yet - its cleanup in progress.
>
> type correctness I do believe is an issue and code readability as well
> so both fixing the type and that name is relevant.
>
> As Wolfram Sang <wsa@...-dreams.de> put it:
> <snip>
>  'ret' being an int is kind of an idiom, so I'd rather see the variable
>  renamed, too, like the other patches do.
> <snip>
> [http://lkml.iu.edu/hypermail/linux/kernel/1502.1/00084.html]
>
> regarding causing problems - it is hard to say - type missmatch
> may go without problems for a long time and then pop up in strange
> corner cases. But you are right that it is not fixing any currently
> inown incorrect behavior.
>
> The motivation for cleaning this up is also to make static code checkers
> happy which eases scanning for incorrect API usage and general bug-hunting,

Ok, added to our testing branch

Thanks
Yan, Zheng

>
> thx!
> hofrat
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