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Commit b8fd9983 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
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sysvipc: unteach ids->next_id for !CHECKPOINT_RESTORE 

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
03f59566 ("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: default avatarDavidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e35c4c64

include/linux/ipc_namespace.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

};

ipc/util.c

+45 −15
Original line number Diff line number Diff line
@@ -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;

}

ipc/util.h

+0 −5
Original line number Diff line number Diff line
@@ -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;