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Rao" , Anil S Keshavamurthy , "David S. Miller" , Masami Hiramatsu , Steven Rostedt , Mark Rutland Cc: Jiri Olsa , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Vlastimil Babka X-Mailer: b4 0.13.0 X-Spam-Flag: NO X-Spam-Score: -6.80 X-Spam-Level: X-Spamd-Result: default: False [-6.80 / 50.00]; REPLY(-4.00)[]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; RCPT_COUNT_TWELVE(0.00)[20]; FREEMAIL_TO(0.00)[gmail.com,linux.com,google.com,kernel.org,iogearbox.net,linux.ibm.com,intel.com,davemloft.net,goodmis.org,arm.com]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; MID_RHS_MATCH_FROM(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[kernel.org,linux.dev,gmail.com,vger.kernel.org,kvack.org,suse.cz]; R_RATELIMIT(0.00)[to_ip_from(RL5nkphuxq5kxo98ppmuqoc8wo)]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCVD_COUNT_TWO(0.00)[2]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] Some fault injection sites are placed in hotpaths and incur overhead even if not enabled, due to one or more function calls leading up to should_fail_ex() that returns false due to attr->probability == 0. This overhead can be eliminated if the outermost call into the checks is guarded with a static key, so add support for that. The framework should be told that such static key exist for a fault_attr, by initializing fault_attr->active with the static key address. When it's not NULL, enable the static key from setup_fault_attr() when the fault probability is non-zero. Also wire up writing into debugfs "probability" file to enable or disable the static key when transitioning between zero and non-zero probability. For now, do not add configfs interface support as the immediate plan is to leverage this for should_failslab() and should_fail_alloc_page() after other necessary preparatory changes, and none of the configfs based fault injection users. Signed-off-by: Vlastimil Babka --- include/linux/fault-inject.h | 7 ++++++- lib/fault-inject.c | 43 ++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 48 insertions(+), 2 deletions(-) diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h index 6d5edef09d45..cfe75cc1bac4 100644 --- a/include/linux/fault-inject.h +++ b/include/linux/fault-inject.h @@ -9,6 +9,7 @@ #include #include #include +#include /* * For explanation of the elements of this struct, see @@ -30,13 +31,14 @@ struct fault_attr { unsigned long count; struct ratelimit_state ratelimit_state; struct dentry *dname; + struct static_key *active; }; enum fault_flags { FAULT_NOWARN = 1 << 0, }; -#define FAULT_ATTR_INITIALIZER { \ +#define FAULT_ATTR_INITIALIZER_KEY(_key) { \ .interval = 1, \ .times = ATOMIC_INIT(1), \ .require_end = ULONG_MAX, \ @@ -44,8 +46,11 @@ enum fault_flags { .ratelimit_state = RATELIMIT_STATE_INIT_DISABLED, \ .verbose = 2, \ .dname = NULL, \ + .active = (_key), \ } +#define FAULT_ATTR_INITIALIZER FAULT_ATTR_INITIALIZER_KEY(NULL) + #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER int setup_fault_attr(struct fault_attr *attr, char *str); bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags); diff --git a/lib/fault-inject.c b/lib/fault-inject.c index d608f9b48c10..93c46d2ec106 100644 --- a/lib/fault-inject.c +++ b/lib/fault-inject.c @@ -35,6 +35,9 @@ int setup_fault_attr(struct fault_attr *attr, char *str) atomic_set(&attr->times, times); atomic_set(&attr->space, space); + if (probability != 0 && attr->active) + static_key_slow_inc(attr->active); + return 1; } EXPORT_SYMBOL_GPL(setup_fault_attr); @@ -166,6 +169,12 @@ EXPORT_SYMBOL_GPL(should_fail); #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS +/* + * Protect updating probability from debugfs as that may trigger static key + * changes when changing between zero and non-zero. + */ +static DEFINE_MUTEX(probability_mutex); + static int debugfs_ul_set(void *data, u64 val) { *(unsigned long *)data = val; @@ -186,6 +195,38 @@ static void debugfs_create_ul(const char *name, umode_t mode, debugfs_create_file(name, mode, parent, value, &fops_ul); } +static int debugfs_prob_set(void *data, u64 val) +{ + struct fault_attr *attr = data; + + mutex_lock(&probability_mutex); + + if (attr->active) { + if (attr->probability != 0 && val == 0) { + static_key_slow_dec(attr->active); + } else if (attr->probability == 0 && val != 0) { + static_key_slow_inc(attr->active); + } + } + + attr->probability = val; + + mutex_unlock(&probability_mutex); + + return 0; +} + +static int debugfs_prob_get(void *data, u64 *val) +{ + struct fault_attr *attr = data; + + *val = attr->probability; + + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(fops_prob, debugfs_prob_get, debugfs_prob_set, "%llu\n"); + #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER static int debugfs_stacktrace_depth_set(void *data, u64 val) @@ -218,7 +259,7 @@ struct dentry *fault_create_debugfs_attr(const char *name, if (IS_ERR(dir)) return dir; - debugfs_create_ul("probability", mode, dir, &attr->probability); + debugfs_create_file("probability", mode, dir, &attr, &fops_prob); debugfs_create_ul("interval", mode, dir, &attr->interval); debugfs_create_atomic_t("times", mode, dir, &attr->times); debugfs_create_atomic_t("space", mode, dir, &attr->space);