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SUNRPC: Cache deferral injection

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Cache deferral injection stress-tests the cache deferral logic as
well as upper layer protocol deferred request handlers. This
facility is for developers and professional testers to ensure
coverage of the rqst deferral code paths. To date, we haven't
had an adequate way to ensure these code paths are covered
during testing, short of temporary code changes to force their
use.

A file called /sys/kernel/debug/fail_sunrpc/ignore-cache-wait
enables administrators to disable cache deferral injection while
allowing other types of sunrpc errors to be injected. The default
setting is that cache deferral injection is enabled (ignore=false).

To enable support for cache deferral injection,
CONFIG_FAULT_INJECTION, CONFIG_FAULT_INJECTION_DEBUG_FS, and
CONFIG_SUNRPC_DEBUG must all be set to "Y".

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2022-03-31 15:30:10 -04:00
parent 45cb7955c1
commit 37324e6bb1
3 changed files with 21 additions and 2 deletions
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18
net/sunrpc/cache.c
View File

@ -33,7 +33,9 @@
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <trace/events/sunrpc.h>
#include "netns.h"
#include "fail.h"
#define RPCDBG_FACILITY RPCDBG_CACHE
@ -688,16 +690,30 @@ static void cache_limit_defers(void)
discard->revisit(discard, 1);
}
#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
static inline bool cache_defer_immediately(void)
{
return !fail_sunrpc.ignore_cache_wait &&
should_fail(&fail_sunrpc.attr, 1);
}
#else
static inline bool cache_defer_immediately(void)
{
return false;
}
#endif
/* Return true if and only if a deferred request is queued. */
static bool cache_defer_req(struct cache_req *req, struct cache_head *item)
{
struct cache_deferred_req *dreq;
if (req->thread_wait) {
if (!cache_defer_immediately()) {
cache_wait_req(req, item);
if (!test_bit(CACHE_PENDING, &item->flags))
return false;
}
dreq = req->defer(req);
if (dreq == NULL)
return false;

3
net/sunrpc/debugfs.c
View File

@ -262,6 +262,9 @@ static void fail_sunrpc_init(void)
debugfs_create_bool("ignore-server-disconnect", S_IFREG | 0600, dir,
&fail_sunrpc.ignore_server_disconnect);
debugfs_create_bool("ignore-cache-wait", S_IFREG | 0600, dir,
&fail_sunrpc.ignore_cache_wait);
}
#else
static void fail_sunrpc_init(void)

2
net/sunrpc/fail.h
View File

@ -14,8 +14,8 @@ struct fail_sunrpc_attr {
struct fault_attr attr;
bool ignore_client_disconnect;
bool ignore_server_disconnect;
bool ignore_cache_wait;
};
extern struct fail_sunrpc_attr fail_sunrpc;