linux-kernel - Re: [PATCH v2] ipc: convert to idr

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Date:	Thu, 7 Feb 2013 20:15:36 +0100
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] ipc: convert to idr_alloc()

On Thu, Feb 7, 2013 at 5:14 PM, Tejun Heo <tj@...nel.org> wrote:
> Convert to the much saner new idr interface.
>
> The new interface doesn't directly translate to the way idr_pre_get()
> was used around ipc_addid() as preloading disables preemption.  From
> my cursory reading, it seems like we should be able to do all
> allocation from ipc_addid(), so I moved it there.  Can you please
> check whether this would be okay?  If this is wrong and ipc_addid()
> should be allowed to be called from non-sleepable context, I'd suggest
> allocating id itself in the outer functions and later install the
> pointer using idr_replace().
>
> Only compile tested.
>
> v2: The v1 conversion of ipcget_public() was incorrect.  As
>     idr_pre_get() returns 0 for -ENOMEM failure, @err should have been
>     initialized to 1 not 0.  As the function doesn't do preloading
>     itself anymore, there's no point in the error handling path.
>     Simply remove the -ENOMEM path.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: Sedat Dilek <sedat.dilek@...il.com>
> Cc: Stanislav Kinsbursky <skinsbursky@...allels.com>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> Cc: James Morris <jmorris@...ei.org>
> ---
> Yeah, I messed up the ipcget_public() conversion.  Can you please test
> this one?
>

Tested-by: Sedat Dilek <sedat.dilek@...il.com> [ The idr-i2c (v2) fix as well! ]

See also file attachments...

- Sedat -

> Thanks.
>
>  ipc/util.c |   30 +++++++++---------------------
>  1 file changed, 9 insertions(+), 21 deletions(-)
>
> --- a/ipc/util.c
> +++ b/ipc/util.c
> @@ -252,7 +252,7 @@ int ipc_addid(struct ipc_ids* ids, struc
>  {
>         kuid_t euid;
>         kgid_t egid;
> -       int id, err;
> +       int id;
>         int next_id = ids->next_id;
>
>         if (size > IPCMNI)
> @@ -261,17 +261,21 @@ int ipc_addid(struct ipc_ids* ids, struc
>         if (ids->in_use >= size)
>                 return -ENOSPC;
>
> +       idr_preload(GFP_KERNEL);
> +
>         spin_lock_init(&new->lock);
>         new->deleted = 0;
>         rcu_read_lock();
>         spin_lock(&new->lock);
>
> -       err = idr_get_new_above(&ids->ipcs_idr, new,
> -                               (next_id < 0) ? 0 : ipcid_to_idx(next_id), &id);
> -       if (err) {
> +       id = idr_alloc(&ids->ipcs_idr, new,
> +                      (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
> +                      GFP_NOWAIT);
> +       idr_preload_end();
> +       if (id < 0) {
>                 spin_unlock(&new->lock);
>                 rcu_read_unlock();
> -               return err;
> +               return id;
>         }
>
>         ids->in_use++;
> @@ -307,19 +311,10 @@ static int ipcget_new(struct ipc_namespa
>                 struct ipc_ops *ops, struct ipc_params *params)
>  {
>         int err;
> -retry:
> -       err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
> -
> -       if (!err)
> -               return -ENOMEM;
>
>         down_write(&ids->rw_mutex);
>         err = ops->getnew(ns, params);
>         up_write(&ids->rw_mutex);
> -
> -       if (err == -EAGAIN)
> -               goto retry;
> -
>         return err;
>  }
>
> @@ -376,8 +371,6 @@ static int ipcget_public(struct ipc_name
>         struct kern_ipc_perm *ipcp;
>         int flg = params->flg;
>         int err;
> -retry:
> -       err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
>
>         /*
>          * Take the lock as a writer since we are potentially going to add
> @@ -389,8 +382,6 @@ retry:
>                 /* key not used */
>                 if (!(flg & IPC_CREAT))
>                         err = -ENOENT;
> -               else if (!err)
> -                       err = -ENOMEM;
>                 else
>                         err = ops->getnew(ns, params);
>         } else {
> @@ -413,9 +404,6 @@ retry:
>         }
>         up_write(&ids->rw_mutex);
>
> -       if (err == -EAGAIN)
> -               goto retry;
> -
>         return err;
>  }
>

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