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sysvipc: unteach ids->next_id for !CHECKPOINT_RESTORE

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Patch series "sysvipc: ipc-key management improvements".

Here are a few improvements I spotted while eyeballing Guillaume's
rhashtable implementation for ipc keys.  The first and fourth patches
are the interesting ones, the middle two are trivial.

This patch (of 4):

The next_id object-allocation functionality was introduced in commit
03f5956680 ("ipc: add sysctl to specify desired next object id").

Given that these new entries are _only_ exported under the
CONFIG_CHECKPOINT_RESTORE option, there is no point for the common case
to even know about ->next_id.  As such rewrite ipc_buildid() such that
it can do away with the field as well as unnecessary branches when
adding a new identifier.  The end result also better differentiates both
cases, so the code ends up being cleaner; albeit the small duplications
regarding the default case.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170831172049.14576-2-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2017-11-17 15:31:08 -08:00 committed by Linus Torvalds
parent e35c4c64fe
commit b8fd998384
3 changed files with 47 additions and 20 deletions
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2
include/linux/ipc_namespace.h
View File

@ -19,7 +19,9 @@ struct ipc_ids {
bool tables_initialized;
struct rw_semaphore rwsem;
struct idr ipcs_idr;
#ifdef CONFIG_CHECKPOINT_RESTORE
int next_id;
#endif
struct rhashtable key_ht;
};

60
ipc/util.c
View File

@ -116,13 +116,15 @@ int ipc_init_ids(struct ipc_ids *ids)
int err;
ids->in_use = 0;
ids->seq = 0;
ids->next_id = -1;
init_rwsem(&ids->rwsem);
err = rhashtable_init(&ids->key_ht, &ipc_kht_params);
if (err)
return err;
idr_init(&ids->ipcs_idr);
ids->tables_initialized = true;
#ifdef CONFIG_CHECKPOINT_RESTORE
ids->next_id = -1;
#endif
return 0;
}
@ -216,6 +218,46 @@ int ipc_get_maxid(struct ipc_ids *ids)
return max_id;
}
#ifdef CONFIG_CHECKPOINT_RESTORE
/*
* Specify desired id for next allocated IPC object.
*/
#define ipc_idr_alloc(ids, new) \
idr_alloc(&(ids)->ipcs_idr, (new), \
(ids)->next_id < 0 ? 0 : ipcid_to_idx((ids)->next_id),\
0, GFP_NOWAIT)
static inline int ipc_buildid(int id, struct ipc_ids *ids,
struct kern_ipc_perm *new)
{
if (ids->next_id < 0) { /* default, behave as !CHECKPOINT_RESTORE */
new->seq = ids->seq++;
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
} else {
new->seq = ipcid_to_seqx(ids->next_id);
ids->next_id = -1;
}
return SEQ_MULTIPLIER * new->seq + id;
}
#else
#define ipc_idr_alloc(ids, new) \
idr_alloc(&(ids)->ipcs_idr, (new), 0, 0, GFP_NOWAIT)
static inline int ipc_buildid(int id, struct ipc_ids *ids,
struct kern_ipc_perm *new)
{
new->seq = ids->seq++;
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
return SEQ_MULTIPLIER * new->seq + id;
}
#endif /* CONFIG_CHECKPOINT_RESTORE */
/**
* ipc_addid - add an ipc identifier
* @ids: ipc identifier set
@ -234,7 +276,6 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
kuid_t euid;
kgid_t egid;
int id, err;
int next_id = ids->next_id;
if (size > IPCMNI)
size = IPCMNI;
@ -254,9 +295,7 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
new->cuid = new->uid = euid;
new->gid = new->cgid = egid;
id = idr_alloc(&ids->ipcs_idr, new,
(next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
GFP_NOWAIT);
id = ipc_idr_alloc(ids, new);
idr_preload_end();
if (id >= 0 && new->key != IPC_PRIVATE) {
@ -274,17 +313,8 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
}
ids->in_use++;
new->id = ipc_buildid(id, ids, new);
if (next_id < 0) {
new->seq = ids->seq++;
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
} else {
new->seq = ipcid_to_seqx(next_id);
ids->next_id = -1;
}
new->id = ipc_buildid(id, new->seq);
return id;
}

5
ipc/util.h
View File

@ -146,11 +146,6 @@ extern struct msg_msg *load_msg(const void __user *src, size_t len);
extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
extern int store_msg(void __user *dest, struct msg_msg *msg, size_t len);
static inline int ipc_buildid(int id, int seq)
{
return SEQ_MULTIPLIER * seq + id;
}
static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
{
return uid / SEQ_MULTIPLIER != ipcp->seq;