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Date: Sun, 18 Sep 2016 16:38:37 -0400
From: James Simmons <jsimmons@...radead.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
devel@...verdev.osuosl.org,
Andreas Dilger <andreas.dilger@...el.com>,
Oleg Drokin <oleg.drokin@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Lustre Development List <lustre-devel@...ts.lustre.org>,
Andreas Dilger <andreas.dilger@...el.com>,
James Simmons <jsimmons@...radead.org>
Subject: [PATCH 098/124] staging: lustre: lprocfs: cleanup stats locking code
From: Andreas Dilger <andreas.dilger@...el.com>
Add comment blocks on lprocfs_stats_lock() and lprocfs_stats_unlock().
Move common NOPERCPU code out of the switch() statements to reduce
code size and complexity, since it doesn't depend on the opc at all.
Replace switch() in lprocfs_stats_unlock() with a simple if/else,
since the lock opc was already checked in lprocfs_stats_lock().
Add an enum for the lprocfs_stats_lock() operations to make it clear
what the valid values are and allow compiler checking.
Signed-off-by: Andreas Dilger <andreas.dilger@...el.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5946
Reviewed-on: http://review.whamcloud.com/12872
Reviewed-by: Bobi Jam <bobijam@...mail.com>
Reviewed-by: John L. Hammond <john.hammond@...el.com>
Reviewed-by: Oleg Drokin <oleg.drokin@...el.com>
Signed-off-by: James Simmons <jsimmons@...radead.org>
---
.../staging/lustre/lustre/include/lprocfs_status.h | 132 +++++++++++---------
1 files changed, 74 insertions(+), 58 deletions(-)
diff --git a/drivers/staging/lustre/lustre/include/lprocfs_status.h b/drivers/staging/lustre/lustre/include/lprocfs_status.h
index b1a8ca5..cc0713e 100644
--- a/drivers/staging/lustre/lustre/include/lprocfs_status.h
+++ b/drivers/staging/lustre/lustre/include/lprocfs_status.h
@@ -165,8 +165,10 @@ struct lprocfs_percpu {
struct lprocfs_counter lp_cntr[0];
};
-#define LPROCFS_GET_NUM_CPU 0x0001
-#define LPROCFS_GET_SMP_ID 0x0002
+enum lprocfs_stats_lock_ops {
+ LPROCFS_GET_NUM_CPU = 0x0001, /* number allocated per-CPU stats */
+ LPROCFS_GET_SMP_ID = 0x0002, /* current stat to be updated */
+};
enum lprocfs_stats_flags {
LPROCFS_STATS_FLAG_NONE = 0x0000, /* per cpu counter */
@@ -371,77 +373,91 @@ int lprocfs_write_frac_helper(const char __user *buffer,
int lprocfs_read_frac_helper(char *buffer, unsigned long count,
long val, int mult);
int lprocfs_stats_alloc_one(struct lprocfs_stats *stats, unsigned int cpuid);
-/*
- * \return value
- * < 0 : on error (only possible for opc as LPROCFS_GET_SMP_ID)
+
+/**
+ * Lock statistics structure for access, possibly only on this CPU.
+ *
+ * The statistics struct may be allocated with per-CPU structures for
+ * efficient concurrent update (usually only on server-wide stats), or
+ * as a single global struct (e.g. for per-client or per-job statistics),
+ * so the required locking depends on the type of structure allocated.
+ *
+ * For per-CPU statistics, pin the thread to the current cpuid so that
+ * will only access the statistics for that CPU. If the stats structure
+ * for the current CPU has not been allocated (or previously freed),
+ * allocate it now. The per-CPU statistics do not need locking since
+ * the thread is pinned to the CPU during update.
+ *
+ * For global statistics, lock the stats structure to prevent concurrent update.
+ *
+ * \param[in] stats statistics structure to lock
+ * \param[in] opc type of operation:
+ * LPROCFS_GET_SMP_ID: "lock" and return current CPU index
+ * for incrementing statistics for that CPU
+ * LPROCFS_GET_NUM_CPU: "lock" and return number of used
+ * CPU indices to iterate over all indices
+ * \param[out] flags CPU interrupt saved state for IRQ-safe locking
+ *
+ * \retval cpuid of current thread or number of allocated structs
+ * \retval negative on error (only for opc LPROCFS_GET_SMP_ID + per-CPU stats)
*/
-static inline int lprocfs_stats_lock(struct lprocfs_stats *stats, int opc,
+static inline int lprocfs_stats_lock(struct lprocfs_stats *stats,
+ enum lprocfs_stats_lock_ops opc,
unsigned long *flags)
{
- int rc = 0;
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
+ spin_lock_irqsave(&stats->ls_lock, *flags);
+ else
+ spin_lock(&stats->ls_lock);
+ return opc == LPROCFS_GET_NUM_CPU ? 1 : 0;
+ }
switch (opc) {
- default:
- LBUG();
+ case LPROCFS_GET_SMP_ID: {
+ unsigned int cpuid = get_cpu();
+
+ if (unlikely(!stats->ls_percpu[cpuid])) {
+ int rc = lprocfs_stats_alloc_one(stats, cpuid);
- case LPROCFS_GET_SMP_ID:
- if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
- if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
- spin_lock_irqsave(&stats->ls_lock, *flags);
- else
- spin_lock(&stats->ls_lock);
- return 0;
- } else {
- unsigned int cpuid = get_cpu();
-
- if (unlikely(!stats->ls_percpu[cpuid])) {
- rc = lprocfs_stats_alloc_one(stats, cpuid);
- if (rc < 0) {
- put_cpu();
- return rc;
- }
+ if (rc < 0) {
+ put_cpu();
+ return rc;
}
- return cpuid;
}
-
+ return cpuid;
+ }
case LPROCFS_GET_NUM_CPU:
- if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
- if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
- spin_lock_irqsave(&stats->ls_lock, *flags);
- else
- spin_lock(&stats->ls_lock);
- return 1;
- }
return stats->ls_biggest_alloc_num;
+ default:
+ LBUG();
}
}
-static inline void lprocfs_stats_unlock(struct lprocfs_stats *stats, int opc,
+/**
+ * Unlock statistics structure after access.
+ *
+ * Unlock the lock acquired via lprocfs_stats_lock() for global statistics,
+ * or unpin this thread from the current cpuid for per-CPU statistics.
+ *
+ * This function must be called using the same arguments as used when calling
+ * lprocfs_stats_lock() so that the correct operation can be performed.
+ *
+ * \param[in] stats statistics structure to unlock
+ * \param[in] opc type of operation (current cpuid or number of structs)
+ * \param[in] flags CPU interrupt saved state for IRQ-safe locking
+ */
+static inline void lprocfs_stats_unlock(struct lprocfs_stats *stats,
+ enum lprocfs_stats_lock_ops opc,
unsigned long *flags)
{
- switch (opc) {
- default:
- LBUG();
-
- case LPROCFS_GET_SMP_ID:
- if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
- if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
- spin_unlock_irqrestore(&stats->ls_lock, *flags);
- else
- spin_unlock(&stats->ls_lock);
- } else {
- put_cpu();
- }
- return;
-
- case LPROCFS_GET_NUM_CPU:
- if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
- if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
- spin_unlock_irqrestore(&stats->ls_lock, *flags);
- else
- spin_unlock(&stats->ls_lock);
- }
- return;
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_NOPERCPU) {
+ if (stats->ls_flags & LPROCFS_STATS_FLAG_IRQ_SAFE)
+ spin_unlock_irqrestore(&stats->ls_lock, *flags);
+ else
+ spin_unlock(&stats->ls_lock);
+ } else if (opc == LPROCFS_GET_SMP_ID) {
+ put_cpu();
}
}
--
1.7.1
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