From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Simmons Date: Mon, 5 Oct 2020 20:06:15 -0400 Subject: [lustre-devel] [PATCH 36/42] lustre: don't take spinlock to read a 'long'. In-Reply-To: <1601942781-24950-1-git-send-email-jsimmons@infradead.org> References: <1601942781-24950-1-git-send-email-jsimmons@infradead.org> Message-ID: <1601942781-24950-37-git-send-email-jsimmons@infradead.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org From: Mr NeilBrown 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. WC-bug-id: https://jira.whamcloud.com/browse/LU-6142 Lustre-commit: 023a9e4cde5498 ("LU-6142 lustre: don't take spinlock to read a 'long'.") Signed-off-by: Mr NeilBrown Reviewed-on: https://review.whamcloud.com/39743 Reviewed-by: Andreas Dilger Reviewed-by: Arshad Hussain Reviewed-by: James Simmons Signed-off-by: James Simmons --- fs/lustre/llite/lproc_llite.c | 24 ++++++------------------ fs/lustre/mdc/lproc_mdc.c | 7 +------ fs/lustre/osc/lproc_osc.c | 23 ++++++++--------------- 3 files changed, 15 insertions(+), 39 deletions(-) diff --git a/fs/lustre/llite/lproc_llite.c b/fs/lustre/llite/lproc_llite.c index 54db7eb..9b1c392 100644 --- a/fs/lustre/llite/lproc_llite.c +++ b/fs/lustre/llite/lproc_llite.c @@ -326,13 +326,9 @@ 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 scnprintf(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, @@ -374,13 +370,9 @@ 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 scnprintf(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, @@ -419,13 +411,9 @@ 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 scnprintf(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/fs/lustre/mdc/lproc_mdc.c b/fs/lustre/mdc/lproc_mdc.c index d7506ea..662be42 100644 --- a/fs/lustre/mdc/lproc_mdc.c +++ b/fs/lustre/mdc/lproc_mdc.c @@ -44,13 +44,8 @@ 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/fs/lustre/osc/lproc_osc.c b/fs/lustre/osc/lproc_osc.c index 14cbe54..7ea9530 100644 --- a/fs/lustre/osc/lproc_osc.c +++ b/fs/lustre/osc/lproc_osc.c @@ -87,7 +87,7 @@ static ssize_t max_rpcs_in_flight_show(struct kobject *kobj, obd_kset.kobj); struct client_obd *cli = &obd->u.cli; - return sprintf(buf, "%u\n", cli->cl_max_rpcs_in_flight); + return scnprintf(buf, PAGE_SIZE, "%u\n", cli->cl_max_rpcs_in_flight); } static ssize_t max_rpcs_in_flight_store(struct kobject *kobj, @@ -139,13 +139,9 @@ 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 scnprintf(buf, PAGE_SIZE, "%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, @@ -252,7 +248,8 @@ static ssize_t cur_dirty_bytes_show(struct kobject *kobj, obd_kset.kobj); struct client_obd *cli = &obd->u.cli; - return sprintf(buf, "%lu\n", cli->cl_dirty_pages << PAGE_SHIFT); + return scnprintf(buf, PAGE_SIZE, "%lu\n", + cli->cl_dirty_pages << PAGE_SHIFT); } LUSTRE_RO_ATTR(cur_dirty_bytes); @@ -264,7 +261,7 @@ static ssize_t cur_grant_bytes_show(struct kobject *kobj, obd_kset.kobj); struct client_obd *cli = &obd->u.cli; - return sprintf(buf, "%lu\n", cli->cl_avail_grant); + return scnprintf(buf, PAGE_SIZE, "%lu\n", cli->cl_avail_grant); } static ssize_t cur_grant_bytes_store(struct kobject *kobj, @@ -284,12 +281,8 @@ static ssize_t cur_grant_bytes_store(struct kobject *kobj, 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 -EINVAL; - } - spin_unlock(&cli->cl_loi_list_lock); with_imp_locked(obd, imp, rc) if (imp->imp_state == LUSTRE_IMP_FULL) @@ -307,7 +300,7 @@ static ssize_t cur_lost_grant_bytes_show(struct kobject *kobj, obd_kset.kobj); struct client_obd *cli = &obd->u.cli; - return sprintf(buf, "%lu\n", cli->cl_lost_grant); + return scnprintf(buf, PAGE_SIZE, "%lu\n", cli->cl_lost_grant); } LUSTRE_RO_ATTR(cur_lost_grant_bytes); -- 1.8.3.1