From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Date: Tue, 19 Feb 2019 11:09:05 +1100 Subject: [lustre-devel] [PATCH 20/37] lustre: convert rsi_sem to a spinlock. In-Reply-To: <155053473693.24125.6976971762921761309.stgit@noble.brown> References: <155053473693.24125.6976971762921761309.stgit@noble.brown> Message-ID: <155053494585.24125.10207641299012244855.stgit@noble.brown> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org This lock is never held over code that sleeps, and is only ever held for short periods of time. So a simple spinlock is best. Signed-off-by: NeilBrown --- drivers/staging/lustre/lustre/include/obd_class.h | 3 +-- drivers/staging/lustre/lustre/llite/llite_lib.c | 6 +++--- drivers/staging/lustre/lustre/llite/lproc_llite.c | 4 ++-- .../lustre/lustre/obdclass/lprocfs_status.c | 8 ++++---- 4 files changed, 10 insertions(+), 11 deletions(-) diff --git a/drivers/staging/lustre/lustre/include/obd_class.h b/drivers/staging/lustre/lustre/include/obd_class.h index 7c2e248a8110..dd480501d7df 100644 --- a/drivers/staging/lustre/lustre/include/obd_class.h +++ b/drivers/staging/lustre/lustre/include/obd_class.h @@ -1688,12 +1688,11 @@ void statfs_pack(struct obd_statfs *osfs, struct kstatfs *sfs); void statfs_unpack(struct kstatfs *sfs, struct obd_statfs *osfs); /* root squash info */ -struct rw_semaphore; struct root_squash_info { uid_t rsi_uid; gid_t rsi_gid; struct list_head rsi_nosquash_nids; - struct rw_semaphore rsi_sem; + spinlock_t rsi_lock; /* protects rsi_nosquash_nids */ }; /* linux-module.c */ diff --git a/drivers/staging/lustre/lustre/llite/llite_lib.c b/drivers/staging/lustre/lustre/llite/llite_lib.c index e2417cd5aaed..d97abbfddccf 100644 --- a/drivers/staging/lustre/lustre/llite/llite_lib.c +++ b/drivers/staging/lustre/lustre/llite/llite_lib.c @@ -130,7 +130,7 @@ static struct ll_sb_info *ll_init_sbi(void) sbi->ll_squash.rsi_uid = 0; sbi->ll_squash.rsi_gid = 0; INIT_LIST_HEAD(&sbi->ll_squash.rsi_nosquash_nids); - init_rwsem(&sbi->ll_squash.rsi_sem); + spin_lock_init(&sbi->ll_squash.rsi_lock); return sbi; } @@ -2578,7 +2578,7 @@ void ll_compute_rootsquash_state(struct ll_sb_info *sbi) int i; /* Update norootsquash flag */ - down_write(&squash->rsi_sem); + spin_lock(&squash->rsi_lock); if (list_empty(&squash->rsi_nosquash_nids)) { spin_lock(&sbi->ll_lock); sbi->ll_flags &= ~LL_SBI_NOROOTSQUASH; @@ -2606,7 +2606,7 @@ void ll_compute_rootsquash_state(struct ll_sb_info *sbi) sbi->ll_flags &= ~LL_SBI_NOROOTSQUASH; spin_unlock(&sbi->ll_lock); } - up_write(&squash->rsi_sem); + spin_unlock(&squash->rsi_lock); } /** diff --git a/drivers/staging/lustre/lustre/llite/lproc_llite.c b/drivers/staging/lustre/lustre/llite/lproc_llite.c index 78ec0fa65c58..db2fbf1f3a50 100644 --- a/drivers/staging/lustre/lustre/llite/lproc_llite.c +++ b/drivers/staging/lustre/lustre/llite/lproc_llite.c @@ -1133,7 +1133,7 @@ static int ll_nosquash_nids_seq_show(struct seq_file *m, void *v) struct root_squash_info *squash = &sbi->ll_squash; int len; - down_read(&squash->rsi_sem); + spin_lock(&squash->rsi_lock); if (!list_empty(&squash->rsi_nosquash_nids)) { len = cfs_print_nidlist(m->buf + m->count, m->size - m->count, &squash->rsi_nosquash_nids); @@ -1142,7 +1142,7 @@ static int ll_nosquash_nids_seq_show(struct seq_file *m, void *v) } else { seq_puts(m, "NONE\n"); } - up_read(&squash->rsi_sem); + spin_unlock(&squash->rsi_lock); return 0; } diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c index 27d73c95403d..aed33068ff3c 100644 --- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c @@ -1720,10 +1720,10 @@ int lprocfs_wr_nosquash_nids(const char __user *buffer, unsigned long count, if ((len == 4 && !strncmp(kernbuf, "NONE", len)) || (len == 5 && !strncmp(kernbuf, "clear", len))) { /* empty string is special case */ - down_write(&squash->rsi_sem); + spin_lock(&squash->rsi_lock); if (!list_empty(&squash->rsi_nosquash_nids)) cfs_free_nidlist(&squash->rsi_nosquash_nids); - up_write(&squash->rsi_sem); + spin_unlock(&squash->rsi_lock); LCONSOLE_INFO("%s: nosquash_nids is cleared\n", name); kfree(kernbuf); return count; @@ -1740,11 +1740,11 @@ int lprocfs_wr_nosquash_nids(const char __user *buffer, unsigned long count, kfree(kernbuf); kernbuf = NULL; - down_write(&squash->rsi_sem); + spin_lock(&squash->rsi_lock); if (!list_empty(&squash->rsi_nosquash_nids)) cfs_free_nidlist(&squash->rsi_nosquash_nids); list_splice(&tmp, &squash->rsi_nosquash_nids); - up_write(&squash->rsi_sem); + spin_unlock(&squash->rsi_lock); return count;