The patch titled
Subject: ipc/util.c: cleanup and improve sysvipc_find_ipc()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
ipc-utilc-cleanup-and-improve-sysvipc_find_ipc-v3.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ipc-utilc-cleanup-and-improve-sysvipc_find_ipc-v3.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Subject: ipc/util.c: cleanup and improve sysvipc_find_ipc()
Date: Fri, 5 Aug 2022 13:57:33 +0200
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@xxxxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20220805115733.104763-1-manfred@xxxxxxxxxxxxxxxx
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Acked-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Cc: "Eric W . Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: <1vier1@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/util.c | 53 ++++++++++++++++++++++++++++++---------------------
1 file changed, 32 insertions(+), 21 deletions(-)
--- a/ipc/util.c~ipc-utilc-cleanup-and-improve-sysvipc_find_ipc-v3
+++ a/ipc/util.c
@@ -782,28 +782,37 @@ struct pid_namespace *ipc_seq_pid_ns(str
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;
+
+ /* convert from position to idr index -> "-1" */
+ tmpidx = *pos - 1;
- if (max_idx == -1 || pos > max_idx)
- goto out;
+ ipc = idr_get_next(&ids->ipcs_idr, &tmpidx);
+ if (ipc != NULL) {
+ rcu_read_lock();
+ ipc_lock_object(ipc);
- for (; pos <= max_idx; pos++) {
- ipc = idr_find(&ids->ipcs_idr, pos);
- if (ipc != NULL) {
- rcu_read_lock();
- ipc_lock_object(ipc);
- break;
- }
+ /* 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 se
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 s
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)
_
Patches currently in -mm which might be from manfred@xxxxxxxxxxxxxxxx are
ipc-utilc-cleanup-and-improve-sysvipc_find_ipc-v3.patch
