[PATCH 4.19 08/72] 9p: Use a slab for allocating requests

Greg Kroah-Hartman
2019-07-02T08:06:00Z

[ Upstream commit 996d5b4db4b191f2676cf8775565cab8a5e2753b ]

Replace the custom batch allocation with a slab. Use an IDR to store
pointers to the active requests instead of an array. We don't try to
handle P9_NOTAG specially; the IDR will happily shrink all the way back
once the TVERSION call has completed.

Link: http://lkml.kernel.org/r/20180711210225.19730-6-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/9p/client.h | 51 ++-------
net/9p/client.c | 238 ++++++++++++++--------------------------
net/9p/mod.c | 9 +-
3 files changed, 102 insertions(+), 196 deletions(-)

diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 0fa0fbab33b0..a4dc42c53d18 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -64,22 +64,15 @@ enum p9_trans_status {

/**
* enum p9_req_status_t - status of a request
- * @REQ_STATUS_IDLE: request slot unused
* @REQ_STATUS_ALLOC: request has been allocated but not sent
* @REQ_STATUS_UNSENT: request waiting to be sent
* @REQ_STATUS_SENT: request sent to server
* @REQ_STATUS_RCVD: response received from server
* @REQ_STATUS_FLSHD: request has been flushed
* @REQ_STATUS_ERROR: request encountered an error on the client side
- *
- * The @REQ_STATUS_IDLE state is used to mark a request slot as unused
- * but use is actually tracked by the idpool structure which handles tag
- * id allocation.
- *
*/

enum p9_req_status_t {
- REQ_STATUS_IDLE,
REQ_STATUS_ALLOC,
REQ_STATUS_UNSENT,
REQ_STATUS_SENT,
@@ -92,24 +85,12 @@ enum p9_req_status_t {
* struct p9_req_t - request slots
* @status: status of this request slot
* @t_err: transport error
- * @flush_tag: tag of request being flushed (for flush requests)
* @wq: wait_queue for the client to block on for this request
* @tc: the request fcall structure
* @rc: the response fcall structure
* @aux: transport specific data (provided for trans_fd migration)
* @req_list: link for higher level objects to chain requests
- *
- * Transport use an array to track outstanding requests
- * instead of a list. While this may incurr overhead during initial
- * allocation or expansion, it makes request lookup much easier as the
- * tag id is a index into an array. (We use tag+1 so that we can accommodate
- * the -1 tag for the T_VERSION request).
- * This also has the nice effect of only having to allocate wait_queues
- * once, instead of constantly allocating and freeing them. Its possible
- * other resources could benefit from this scheme as well.
- *
*/
-
struct p9_req_t {
int status;
int t_err;
@@ -117,40 +98,26 @@ struct p9_req_t {
struct p9_fcall *tc;
struct p9_fcall *rc;
void *aux;
-
struct list_head req_list;
};

/**
* struct p9_client - per client instance state
- * @lock: protect @fidlist
+ * @lock: protect @fids and @reqs
* @msize: maximum data size negotiated by protocol
- * @dotu: extension flags negotiated by protocol
* @proto_version: 9P protocol version to use
* @trans_mod: module API instantiated with this client
+ * @status: connection state
* @trans: tranport instance state and API
* @fids: All active FID handles
- * @tagpool - transaction id accounting for session
- * @reqs - 2D array of requests
- * @max_tag - current maximum tag id allocated
- * @name - node name used as client id
+ * @reqs: All active requests.
+ * @name: node name used as client id
*
* The client structure is used to keep track of various per-client
* state that has been instantiated.
- * In order to minimize per-transaction overhead we use a
- * simple array to lookup requests instead of a hash table
- * or linked list. In order to support larger number of
- * transactions, we make this a 2D array, allocating new rows
- * when we need to grow the total number of the transactions.
- *
- * Each row is 256 requests and we'll support up to 256 rows for
- * a total of 64k concurrent requests per session.
- *
- * Bugs: duplicated data and potentially unnecessary elements.
*/
-
struct p9_client {
- spinlock_t lock; /* protect client structure */
+ spinlock_t lock;
unsigned int msize;
unsigned char proto_version;
struct p9_trans_module *trans_mod;
@@ -170,10 +137,7 @@ struct p9_client {
} trans_opts;

struct idr fids;
-
- struct p9_idpool *tagpool;
- struct p9_req_t *reqs[P9_ROW_MAXTAG];
- int max_tag;
+ struct idr reqs;

char name[__NEW_UTS_LEN + 1];
};
@@ -279,4 +243,7 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *, const char *, u64 *);
int p9_client_xattrcreate(struct p9_fid *, const char *, u64, int);
int p9_client_readlink(struct p9_fid *fid, char **target);

+int p9_client_init(void);
+void p9_client_exit(void);
+
#endif /* NET_9P_CLIENT_H */
diff --git a/net/9p/client.c b/net/9p/client.c
index 23ec6187dc07..d8949c59d46e 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -248,132 +248,102 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
return fc;
}

+static struct kmem_cache *p9_req_cache;
+
/**
- * p9_tag_alloc - lookup/allocate a request by tag
- * @c: client session to lookup tag within
- * @tag: numeric id for transaction
- *
- * this is a simple array lookup, but will grow the
- * request_slots as necessary to accommodate transaction
- * ids which did not previously have a slot.
- *
- * this code relies on the client spinlock to manage locks, its
- * possible we should switch to something else, but I'd rather
- * stick with something low-overhead for the common case.
+ * p9_req_alloc - Allocate a new request.
+ * @c: Client session.
+ * @type: Transaction type.
+ * @max_size: Maximum packet size for this request.
*
+ * Context: Process context.
+ * Return: Pointer to new request.
*/
-
static struct p9_req_t *
-p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
+p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
{
- unsigned long flags;
- int row, col;
- struct p9_req_t *req;
+ struct p9_req_t *req = kmem_cache_alloc(p9_req_cache, GFP_NOFS);
int alloc_msize = min(c->msize, max_size);
+ int tag;

- /* This looks up the original request by tag so we know which
- * buffer to read the data into */
- tag++;
-
- if (tag >= c->max_tag) {
- spin_lock_irqsave(&c->lock, flags);
- /* check again since original check was outside of lock */
- while (tag >= c->max_tag) {
- row = (tag / P9_ROW_MAXTAG);
- c->reqs[row] = kcalloc(P9_ROW_MAXTAG,
- sizeof(struct p9_req_t), GFP_ATOMIC);
-
- if (!c->reqs[row]) {
- pr_err("Couldn't grow tag array\n");
- spin_unlock_irqrestore(&c->lock, flags);
- return ERR_PTR(-ENOMEM);
- }
- for (col = 0; col < P9_ROW_MAXTAG; col++) {
- req = &c->reqs[row][col];
- req->status = REQ_STATUS_IDLE;
- init_waitqueue_head(&req->wq);
- }
- c->max_tag += P9_ROW_MAXTAG;
- }
- spin_unlock_irqrestore(&c->lock, flags);
- }
- row = tag / P9_ROW_MAXTAG;
- col = tag % P9_ROW_MAXTAG;
+ if (!req)
+ return NULL;

- req = &c->reqs[row][col];
- if (!req->tc)
- req->tc = p9_fcall_alloc(alloc_msize);
- if (!req->rc)
- req->rc = p9_fcall_alloc(alloc_msize);
+ req->tc = p9_fcall_alloc(alloc_msize);
+ req->rc = p9_fcall_alloc(alloc_msize);
if (!req->tc || !req->rc)
- goto grow_failed;
+ goto free;

p9pdu_reset(req->tc);
p9pdu_reset(req->rc);
-
- req->tc->tag = tag-1;
req->status = REQ_STATUS_ALLOC;
+ init_waitqueue_head(&req->wq);
+ INIT_LIST_HEAD(&req->req_list);
+
+ idr_preload(GFP_NOFS);
+ spin_lock_irq(&c->lock);
+ if (type == P9_TVERSION)
+ tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
+ GFP_NOWAIT);
+ else
+ tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
+ req->tc->tag = tag;
+ spin_unlock_irq(&c->lock);
+ idr_preload_end();
+ if (tag < 0)
+ goto free;

return req;

-grow_failed:
- pr_err("Couldn't grow tag array\n");
+free:
kfree(req->tc);
kfree(req->rc);
- req->tc = req->rc = NULL;
+ kmem_cache_free(p9_req_cache, req);
return ERR_PTR(-ENOMEM);
}

/**
- * p9_tag_lookup - lookup a request by tag
- * @c: client session to lookup tag within
- * @tag: numeric id for transaction
+ * p9_tag_lookup - Look up a request by tag.
+ * @c: Client session.
+ * @tag: Transaction ID.
*
+ * Context: Any context.
+ * Return: A request, or %NULL if there is no request with that tag.
*/
-
struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
{
- int row, col;
-
- /* This looks up the original request by tag so we know which
- * buffer to read the data into */
- tag++;
-
- if (tag >= c->max_tag)
- return NULL;
+ struct p9_req_t *req;

- row = tag / P9_ROW_MAXTAG;
- col = tag % P9_ROW_MAXTAG;
+ rcu_read_lock();
+ req = idr_find(&c->reqs, tag);
+ /* There's no refcount on the req; a malicious server could cause
+ * us to dereference a NULL pointer
+ */
+ rcu_read_unlock();

- return &c->reqs[row][col];
+ return req;
}
EXPORT_SYMBOL(p9_tag_lookup);

/**
- * p9_tag_init - setup tags structure and contents
- * @c: v9fs client struct
- *
- * This initializes the tags structure for each client instance.
+ * p9_free_req - Free a request.
+ * @c: Client session.
+ * @r: Request to free.
*
+ * Context: Any context.
*/
-
-static int p9_tag_init(struct p9_client *c)
+static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
{
- int err = 0;
+ unsigned long flags;
+ u16 tag = r->tc->tag;

- c->tagpool = p9_idpool_create();
- if (IS_ERR(c->tagpool)) {
- err = PTR_ERR(c->tagpool);
- goto error;
- }
- err = p9_idpool_get(c->tagpool); /* reserve tag 0 */
- if (err < 0) {
- p9_idpool_destroy(c->tagpool);
- goto error;
- }
- c->max_tag = 0;
-error:
- return err;
+ p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
+ spin_lock_irqsave(&c->lock, flags);
+ idr_remove(&c->reqs, tag);
+ spin_unlock_irqrestore(&c->lock, flags);
+ kfree(r->tc);
+ kfree(r->rc);
+ kmem_cache_free(p9_req_cache, r);
}

/**
@@ -385,52 +355,15 @@ static int p9_tag_init(struct p9_client *c)
*/
static void p9_tag_cleanup(struct p9_client *c)
{
- int row, col;
-
- /* check to insure all requests are idle */
- for (row = 0; row < (c->max_tag/P9_ROW_MAXTAG); row++) {
- for (col = 0; col < P9_ROW_MAXTAG; col++) {
- if (c->reqs[row][col].status != REQ_STATUS_IDLE) {
- p9_debug(P9_DEBUG_MUX,
- "Attempting to cleanup non-free tag %d,%d\n",
- row, col);
- /* TODO: delay execution of cleanup */
- return;
- }
- }
- }
-
- if (c->tagpool) {
- p9_idpool_put(0, c->tagpool); /* free reserved tag 0 */
- p9_idpool_destroy(c->tagpool);
- }
+ struct p9_req_t *req;
+ int id;

- /* free requests associated with tags */
- for (row = 0; row < (c->max_tag/P9_ROW_MAXTAG); row++) {
- for (col = 0; col < P9_ROW_MAXTAG; col++) {
- kfree(c->reqs[row][col].tc);
- kfree(c->reqs[row][col].rc);
- }
- kfree(c->reqs[row]);
+ rcu_read_lock();
+ idr_for_each_entry(&c->reqs, req, id) {
+ pr_info("Tag %d still in use\n", id);
+ p9_free_req(c, req);
}
- c->max_tag = 0;
-}
-
-/**
- * p9_free_req - free a request and clean-up as necessary
- * c: client state
- * r: request to release
- *
- */
-
-static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
-{
- int tag = r->tc->tag;
- p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
-
- r->status = REQ_STATUS_IDLE;
- if (tag != P9_NOTAG && p9_idpool_check(tag, c->tagpool))
- p9_idpool_put(tag, c->tagpool);
+ rcu_read_unlock();
}

/**
@@ -704,7 +637,7 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
int8_t type, int req_size,
const char *fmt, va_list ap)
{
- int tag, err;
+ int err;
struct p9_req_t *req;

p9_debug(P9_DEBUG_MUX, "client %p op %d\n", c, type);
@@ -717,24 +650,17 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
if ((c->status == BeginDisconnect) && (type != P9_TCLUNK))
return ERR_PTR(-EIO);

- tag = P9_NOTAG;
- if (type != P9_TVERSION) {
- tag = p9_idpool_get(c->tagpool);
- if (tag < 0)
- return ERR_PTR(-ENOMEM);
- }
-
- req = p9_tag_alloc(c, tag, req_size);
+ req = p9_tag_alloc(c, type, req_size);
if (IS_ERR(req))
return req;

/* marshall the data */
- p9pdu_prepare(req->tc, tag, type);
+ p9pdu_prepare(req->tc, req->tc->tag, type);
err = p9pdu_vwritef(req->tc, c->proto_version, fmt, ap);
if (err)
goto reterr;
p9pdu_finalize(c, req->tc);
- trace_9p_client_req(c, type, tag);
+ trace_9p_client_req(c, type, req->tc->tag);
return req;
reterr:
p9_free_req(c, req);
@@ -1040,14 +966,11 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)

spin_lock_init(&clnt->lock);
idr_init(&clnt->fids);
-
- err = p9_tag_init(clnt);
- if (err < 0)
- goto free_client;
+ idr_init(&clnt->reqs);

err = parse_opts(options, clnt);
if (err < 0)
- goto destroy_tagpool;
+ goto free_client;

if (!clnt->trans_mod)
clnt->trans_mod = v9fs_get_default_trans();
@@ -1056,7 +979,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
err = -EPROTONOSUPPORT;
p9_debug(P9_DEBUG_ERROR,
"No transport defined or default transport\n");
- goto destroy_tagpool;
+ goto free_client;
}

p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n",
@@ -1086,8 +1009,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
clnt->trans_mod->close(clnt);
put_trans:
v9fs_put_trans(clnt->trans_mod);
-destroy_tagpool:
- p9_idpool_destroy(clnt->tagpool);
free_client:
kfree(clnt);
return ERR_PTR(err);
@@ -2303,3 +2224,14 @@ int p9_client_readlink(struct p9_fid *fid, char **target)
return err;
}
EXPORT_SYMBOL(p9_client_readlink);
+
+int __init p9_client_init(void)
+{
+ p9_req_cache = KMEM_CACHE(p9_req_t, 0);
+ return p9_req_cache ? 0 : -ENOMEM;
+}
+
+void __exit p9_client_exit(void)
+{
+ kmem_cache_destroy(p9_req_cache);
+}
diff --git a/net/9p/mod.c b/net/9p/mod.c
index 253ba824a325..0da56d6af73b 100644
--- a/net/9p/mod.c
+++ b/net/9p/mod.c
@@ -171,11 +171,17 @@ void v9fs_put_trans(struct p9_trans_module *m)
*/
static int __init init_p9(void)
{
+ int ret;
+
+ ret = p9_client_init();
+ if (ret)
+ return ret;
+
p9_error_init();
pr_info("Installing 9P2000 support\n");
p9_trans_fd_init();

- return 0;
+ return ret;
}

/**
@@ -188,6 +194,7 @@ static void __exit exit_p9(void)
pr_info("Unloading 9P2000 support\n");

p9_trans_fd_exit();
+ p9_client_exit();
}

module_init(init_p9)
--
2.20.1