LU-6142 lustre: don't take spinlock to read a 'long'.

Reading a 'long' (or unsigned long) is always an atomic operation.
There is never a need to take a spinlock to just read a single 'long'.

There are several procfs/debugfs/sysfs handlers which needlessly take
a spinlock for this purpose.

This patch:
 - removes the taking of the spinlock
 - changes the printf to scnprintf() as appropriate
 - directly returns the value returned by scnprintf rather than
   storing it in a variable
 - accesses the 'long' as an arg to the scnprintf(), rather than
   introducing a variabe to hold it.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: If4a6454b46844864e1177536a9c7b91e4c97de86
Reviewed-on: https://review.whamcloud.com/39743
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>

diff --git a/lustre/llite/lproc_llite.c b/lustre/llite/lproc_llite.c
index c701e0f..f6a7699 100644 (file)
--- a/lustre/llite/lproc_llite.c
+++ b/lustre/llite/lproc_llite.c
@@ -324,13 +324,9 @@ static ssize_t max_read_ahead_mb_show(struct kobject *kobj,
 {
        struct ll_sb_info *sbi = container_of(kobj, struct ll_sb_info,
                                              ll_kset.kobj);
-       unsigned long ra_max_mb;
 
-       spin_lock(&sbi->ll_lock);
-       ra_max_mb = PAGES_TO_MiB(sbi->ll_ra_info.ra_max_pages);
-       spin_unlock(&sbi->ll_lock);
-
-       return snprintf(buf, PAGE_SIZE, "%lu\n", ra_max_mb);
+       return scnprintf(buf, PAGE_SIZE, "%lu\n",
+                       PAGES_TO_MiB(sbi->ll_ra_info.ra_max_pages));
 }
 
 static ssize_t max_read_ahead_mb_store(struct kobject *kobj,
@@ -371,13 +367,9 @@ static ssize_t max_read_ahead_per_file_mb_show(struct kobject *kobj,
 {
        struct ll_sb_info *sbi = container_of(kobj, struct ll_sb_info,
                                              ll_kset.kobj);
-       unsigned long ra_max_file_mb;
 
-       spin_lock(&sbi->ll_lock);
-       ra_max_file_mb = PAGES_TO_MiB(sbi->ll_ra_info.ra_max_pages_per_file);
-       spin_unlock(&sbi->ll_lock);
-
-       return snprintf(buf, PAGE_SIZE, "%lu\n", ra_max_file_mb);
+       return scnprintf(buf, PAGE_SIZE, "%lu\n",
+                        PAGES_TO_MiB(sbi->ll_ra_info.ra_max_pages_per_file));
 }
 
 static ssize_t max_read_ahead_per_file_mb_store(struct kobject *kobj,
@@ -415,13 +407,9 @@ static ssize_t max_read_ahead_whole_mb_show(struct kobject *kobj,
 {
        struct ll_sb_info *sbi = container_of(kobj, struct ll_sb_info,
                                              ll_kset.kobj);
-       unsigned long ra_max_whole_mb;
-
-       spin_lock(&sbi->ll_lock);
-       ra_max_whole_mb = PAGES_TO_MiB(sbi->ll_ra_info.ra_max_read_ahead_whole_pages);
-       spin_unlock(&sbi->ll_lock);
 
-       return snprintf(buf, PAGE_SIZE, "%lu\n", ra_max_whole_mb);
+       return scnprintf(buf, PAGE_SIZE, "%lu\n",
+                        PAGES_TO_MiB(sbi->ll_ra_info.ra_max_read_ahead_whole_pages));
 }
 
 static ssize_t max_read_ahead_whole_mb_store(struct kobject *kobj,

diff --git a/lustre/mdc/lproc_mdc.c b/lustre/mdc/lproc_mdc.c
index 9de5c70..a2ca754 100644 (file)
--- a/lustre/mdc/lproc_mdc.c
+++ b/lustre/mdc/lproc_mdc.c
@@ -149,13 +149,8 @@ static int mdc_max_dirty_mb_seq_show(struct seq_file *m, void *v)
 {
        struct obd_device *obd = m->private;
        struct client_obd *cli = &obd->u.cli;
-       unsigned long val;
 
-       spin_lock(&cli->cl_loi_list_lock);
-       val = PAGES_TO_MiB(cli->cl_dirty_max_pages);
-       spin_unlock(&cli->cl_loi_list_lock);
-
-       seq_printf(m, "%lu\n", val);
+       seq_printf(m, "%lu\n", PAGES_TO_MiB(cli->cl_dirty_max_pages));
        return 0;
 }
 

diff --git a/lustre/osc/lproc_osc.c b/lustre/osc/lproc_osc.c
index 498e03f..a497228 100644 (file)
--- a/lustre/osc/lproc_osc.c
+++ b/lustre/osc/lproc_osc.c
@@ -85,12 +85,8 @@ static ssize_t max_rpcs_in_flight_show(struct kobject *kobj,
        struct obd_device *obd = container_of(kobj, struct obd_device,
                                              obd_kset.kobj);
        struct client_obd *cli = &obd->u.cli;
-       ssize_t len;
 
-       spin_lock(&cli->cl_loi_list_lock);
-       len = sprintf(buf, "%u\n", cli->cl_max_rpcs_in_flight);
-       spin_unlock(&cli->cl_loi_list_lock);
-       return len;
+       return  scnprintf(buf, PAGE_SIZE, "%u\n", cli->cl_max_rpcs_in_flight);
 }
 
 static ssize_t max_rpcs_in_flight_store(struct kobject *kobj,
@@ -142,13 +138,9 @@ static ssize_t max_dirty_mb_show(struct kobject *kobj,
        struct obd_device *obd = container_of(kobj, struct obd_device,
                                              obd_kset.kobj);
        struct client_obd *cli = &obd->u.cli;
-       unsigned long val;
 
-       spin_lock(&cli->cl_loi_list_lock);
-       val = PAGES_TO_MiB(cli->cl_dirty_max_pages);
-       spin_unlock(&cli->cl_loi_list_lock);
-
-       return sprintf(buf, "%lu\n", val);
+       return scnprintf(buf, PAGE_SIZE, "%lu\n",
+                        PAGES_TO_MiB(cli->cl_dirty_max_pages));
 }
 
 static ssize_t max_dirty_mb_store(struct kobject *kobj,
@@ -254,13 +246,9 @@ static ssize_t cur_dirty_bytes_show(struct kobject *kobj,
        struct obd_device *obd = container_of(kobj, struct obd_device,
                                              obd_kset.kobj);
        struct client_obd *cli = &obd->u.cli;
-       ssize_t len;
-
-       spin_lock(&cli->cl_loi_list_lock);
-       len = sprintf(buf, "%lu\n", cli->cl_dirty_pages << PAGE_SHIFT);
-       spin_unlock(&cli->cl_loi_list_lock);
 
-       return len;
+       return scnprintf(buf, PAGE_SIZE, "%lu\n",
+                        cli->cl_dirty_pages << PAGE_SHIFT);
 }
 LUSTRE_RO_ATTR(cur_dirty_bytes);
 
@@ -269,9 +257,7 @@ static int osc_cur_grant_bytes_seq_show(struct seq_file *m, void *v)
        struct obd_device *obd = m->private;
        struct client_obd *cli = &obd->u.cli;
 
-       spin_lock(&cli->cl_loi_list_lock);
        seq_printf(m, "%lu\n", cli->cl_avail_grant);
-       spin_unlock(&cli->cl_loi_list_lock);
        return 0;
 }
 
@@ -302,13 +288,8 @@ static ssize_t osc_cur_grant_bytes_seq_write(struct file *file,
                return rc;
 
        /* this is only for shrinking grant */
-       spin_lock(&cli->cl_loi_list_lock);
-       if (val >= cli->cl_avail_grant) {
-               spin_unlock(&cli->cl_loi_list_lock);
+       if (val >= cli->cl_avail_grant)
                return 0;
-       }
-
-       spin_unlock(&cli->cl_loi_list_lock);
 
        with_imp_locked(obd, imp, rc)
                if (imp->imp_state == LUSTRE_IMP_FULL)
@@ -325,12 +306,8 @@ static ssize_t cur_lost_grant_bytes_show(struct kobject *kobj,
        struct obd_device *obd = container_of(kobj, struct obd_device,
                                              obd_kset.kobj);
        struct client_obd *cli = &obd->u.cli;
-       ssize_t len;
 
-       spin_lock(&cli->cl_loi_list_lock);
-       len = sprintf(buf, "%lu\n", cli->cl_lost_grant);
-       spin_unlock(&cli->cl_loi_list_lock);
-       return len;
+       return scnprintf(buf, PAGE_SIZE, "%lu\n", cli->cl_lost_grant);
 }
 LUSTRE_RO_ATTR(cur_lost_grant_bytes);