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ipc/util.c: cleanup and improve sysvipc_find_ipc()

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sysvipc_find_ipc() can be simplified further:

- It uses a for() loop to locate the next entry in the idr.
  This can be replaced with idr_get_next().

- It receives two parameters (pos - which is actually
  an idr index and not a position, and new_pos, which
  is really a position).
  One parameter is sufficient.

Link: https://lore.kernel.org/all/20210903052020.3265-3-manfred@colorfullife.com/
Link: https://lkml.kernel.org/r/20220805115733.104763-1-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Waiman Long <longman@redhat.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: <1vier1@web.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2022-08-05 13:57:33 +02:00 committed by Andrew Morton
parent 765f2bf04f
commit 58b5c20336
1 changed files with 32 additions and 21 deletions
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53
ipc/util.c
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@ -782,28 +782,37 @@ struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
return iter->pid_ns;
}
/*
* This routine locks the ipc structure found at least at position pos.
/**
* sysvipc_find_ipc - Find and lock the ipc structure based on seq pos
* @ids: ipc identifier set
* @pos: expected position
*
* The function finds an ipc structure, based on the sequence file
* position @pos. If there is no ipc structure at position @pos, then
* the successor is selected.
* If a structure is found, then it is locked (both rcu_read_lock() and
* ipc_lock_object()) and @pos is set to the position needed to locate
* the found ipc structure.
* If nothing is found (i.e. EOF), @pos is not modified.
*
* The function returns the found ipc structure, or NULL at EOF.
*/
static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
loff_t *new_pos)
static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t *pos)
{
struct kern_ipc_perm *ipc = NULL;
int max_idx = ipc_get_maxidx(ids);
int tmpidx;
struct kern_ipc_perm *ipc;
if (max_idx == -1 || pos > max_idx)
goto out;
/* convert from position to idr index -> "-1" */
tmpidx = *pos - 1;
for (; pos <= max_idx; pos++) {
ipc = idr_find(&ids->ipcs_idr, pos);
if (ipc != NULL) {
rcu_read_lock();
ipc_lock_object(ipc);
break;
}
ipc = idr_get_next(&ids->ipcs_idr, &tmpidx);
if (ipc != NULL) {
rcu_read_lock();
ipc_lock_object(ipc);
/* convert from idr index to position -> "+1" */
*pos = tmpidx + 1;
}
out:
*new_pos = pos + 1;
return ipc;
}
@ -817,11 +826,13 @@ static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
/* Next -> search for *pos+1 */
(*pos)++;
return sysvipc_find_ipc(&iter->ns->ids[iface->ids], pos);
}
/*
* File positions: pos 0 -> header, pos n -> ipc id = n - 1.
* File positions: pos 0 -> header, pos n -> ipc idx = n - 1.
* SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
@ -846,8 +857,8 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
if (*pos == 0)
return SEQ_START_TOKEN;
/* Find the (pos-1)th ipc */
return sysvipc_find_ipc(ids, *pos - 1, pos);
/* Otherwise return the correct ipc structure */
return sysvipc_find_ipc(ids, pos);
}
static void sysvipc_proc_stop(struct seq_file *s, void *it)