[PATCH 09/10] staging: lustre: remove page_collection::pc_lock in libcfs

James Simmons
2015-11-04T18:40:32Z

From: Liang Zhen <liang.zhen@intel.com>

page_collection::pc_lock is supposed to protect race between
functions called by smp_call_function(), however we don't have
this use-case for ages and page_collection only lives in stack
of thread, so it is safe to remove it.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3055
Reviewed-on: http://review.whamcloud.com/7660
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Sebastien Buisson <sebastien.buisson@bull.net>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---
drivers/staging/lustre/lustre/libcfs/tracefile.c | 14 --------------
drivers/staging/lustre/lustre/libcfs/tracefile.h | 8 --------
2 files changed, 0 insertions(+), 22 deletions(-)

diff --git a/drivers/staging/lustre/lustre/libcfs/tracefile.c b/drivers/staging/lustre/lustre/libcfs/tracefile.c
index 973c7c2..6fe7dfb 100644
--- a/drivers/staging/lustre/lustre/libcfs/tracefile.c
+++ b/drivers/staging/lustre/lustre/libcfs/tracefile.c
@@ -199,7 +199,6 @@ static void cfs_tcd_shrink(struct cfs_trace_cpu_data *tcd)
pgcount + 1, tcd->tcd_cur_pages);

INIT_LIST_HEAD(&pc.pc_pages);
- spin_lock_init(&pc.pc_lock);

list_for_each_entry_safe(tage, tmp, &tcd->tcd_pages, linkage) {
if (pgcount-- == 0)
@@ -522,7 +521,6 @@ static void collect_pages_on_all_cpus(struct page_collection *pc)
struct cfs_trace_cpu_data *tcd;
int i, cpu;

- spin_lock(&pc->pc_lock);
for_each_possible_cpu(cpu) {
cfs_tcd_for_each_type_lock(tcd, i, cpu) {
list_splice_init(&tcd->tcd_pages, &pc->pc_pages);
@@ -534,7 +532,6 @@ static void collect_pages_on_all_cpus(struct page_collection *pc)
}
}
}
- spin_unlock(&pc->pc_lock);
}

static void collect_pages(struct page_collection *pc)
@@ -555,7 +552,6 @@ static void put_pages_back_on_all_cpus(struct page_collection *pc)
struct cfs_trace_page *tmp;
int i, cpu;

- spin_lock(&pc->pc_lock);
for_each_possible_cpu(cpu) {
cfs_tcd_for_each_type_lock(tcd, i, cpu) {
cur_head = tcd->tcd_pages.next;
@@ -573,7 +569,6 @@ static void put_pages_back_on_all_cpus(struct page_collection *pc)
}
}
}
- spin_unlock(&pc->pc_lock);
}

static void put_pages_back(struct page_collection *pc)
@@ -592,7 +587,6 @@ static void put_pages_on_tcd_daemon_list(struct page_collection *pc,
struct cfs_trace_page *tage;
struct cfs_trace_page *tmp;

- spin_lock(&pc->pc_lock);
list_for_each_entry_safe(tage, tmp, &pc->pc_pages, linkage) {

__LASSERT_TAGE_INVARIANT(tage);
@@ -616,7 +610,6 @@ static void put_pages_on_tcd_daemon_list(struct page_collection *pc,
tcd->tcd_cur_daemon_pages--;
}
}
- spin_unlock(&pc->pc_lock);
}

static void put_pages_on_daemon_list(struct page_collection *pc)
@@ -636,8 +629,6 @@ void cfs_trace_debug_print(void)
struct cfs_trace_page *tage;
struct cfs_trace_page *tmp;

- spin_lock_init(&pc.pc_lock);
-
pc.pc_want_daemon_pages = 1;
collect_pages(&pc);
list_for_each_entry_safe(tage, tmp, &pc.pc_pages, linkage) {
@@ -692,7 +683,6 @@ int cfs_tracefile_dump_all_pages(char *filename)
goto out;
}

- spin_lock_init(&pc.pc_lock);
pc.pc_want_daemon_pages = 1;
collect_pages(&pc);
if (list_empty(&pc.pc_pages)) {
@@ -739,8 +729,6 @@ void cfs_trace_flush_pages(void)
struct cfs_trace_page *tage;
struct cfs_trace_page *tmp;

- spin_lock_init(&pc.pc_lock);
-
pc.pc_want_daemon_pages = 1;
collect_pages(&pc);
list_for_each_entry_safe(tage, tmp, &pc.pc_pages, linkage) {
@@ -970,7 +958,6 @@ static int tracefiled(void *arg)
/* we're started late enough that we pick up init's fs context */
/* this is so broken in uml? what on earth is going on? */

- spin_lock_init(&pc.pc_lock);
complete(&tctl->tctl_start);

while (1) {
@@ -1170,7 +1157,6 @@ static void cfs_trace_cleanup(void)
struct page_collection pc;

INIT_LIST_HEAD(&pc.pc_pages);
- spin_lock_init(&pc.pc_lock);

trace_cleanup_on_all_cpus();

diff --git a/drivers/staging/lustre/lustre/libcfs/tracefile.h b/drivers/staging/lustre/lustre/libcfs/tracefile.h
index cb7a396..de37fb7 100644
--- a/drivers/staging/lustre/lustre/libcfs/tracefile.h
+++ b/drivers/staging/lustre/lustre/libcfs/tracefile.h
@@ -196,14 +196,6 @@ extern union cfs_trace_data_union (*cfs_trace_data[TCD_MAX_TYPES])[NR_CPUS];
struct page_collection {
struct list_head pc_pages;
/*
- * spin-lock protecting ->pc_pages. It is taken by smp_call_function()
- * call-back functions. XXX nikita: Which is horrible: all processors
- * receive NMI at the same time only to be serialized by this
- * lock. Probably ->pc_pages should be replaced with an array of
- * NR_CPUS elements accessed locklessly.
- */
- spinlock_t pc_lock;
- /*
* if this flag is set, collect_pages() will spill both
* ->tcd_daemon_pages and ->tcd_pages to the ->pc_pages. Otherwise,
* only ->tcd_pages are spilled.
--
1.7.1