From f0a5268d32a829167cfbd68236c827d58380cbb3 Mon Sep 17 00:00:00 2001
From: Andrea Mazzoleni <amadvance@gmail.com>
Date: Sat, 22 May 2021 10:09:43 +0200
Subject: [PATCH] Avoid to use the filesystem mutex when it's not necessary

This speed-up a bit the check and fix that are monothreads
---
 cmdline/elem.c | 20 ++++++++++++++++----
 cmdline/elem.h |  8 +++++++-
 cmdline/io.c   |  7 +++++++
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/cmdline/elem.c b/cmdline/elem.c
index a597c07d..228a3c81 100644
--- a/cmdline/elem.c
+++ b/cmdline/elem.c
@@ -736,7 +736,7 @@ int dir_name_compare(const void* void_arg, const void* void_data)
 	return strcmp(arg, dir->sub);
 }
 
-struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev, const char* uuid, int skip)
+struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev, const char* uuid, int skip_access)
 {
 	struct snapraid_disk* disk;
 
@@ -750,6 +750,7 @@ struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev
 
 #if HAVE_PTHREAD
 	thread_mutex_init(&disk->fs_mutex, 0);
+	disk->fs_mutex_enabled = 0; /* lock will be enabled at threads start */
 #endif
 
 	disk->smartctl[0] = 0;
@@ -767,7 +768,7 @@ struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev
 	disk->has_unsupported_uuid = *uuid == 0; /* empty UUID means unsupported */
 	disk->had_empty_uuid = 0;
 	disk->mapping_idx = -1;
-	disk->skip_access = skip;
+	disk->skip_access = skip_access;
 	tommy_list_init(&disk->filelist);
 	tommy_list_init(&disk->deletedlist);
 	tommy_hashdyn_init(&disk->inodeset);
@@ -804,10 +805,20 @@ void disk_free(struct snapraid_disk* disk)
 	free(disk);
 }
 
+void disk_start_thread(struct snapraid_disk* disk)
+{
+#if HAVE_PTHREAD
+	disk->fs_mutex_enabled = 1;
+#else
+	(void)disk;
+#endif
+}
+
 static inline void fs_lock(struct snapraid_disk* disk)
 {
 #if HAVE_PTHREAD
-	thread_mutex_lock(&disk->fs_mutex);
+	if (disk->fs_mutex_enabled)
+		thread_mutex_lock(&disk->fs_mutex);
 #else
 	(void)disk;
 #endif
@@ -816,7 +827,8 @@ static inline void fs_lock(struct snapraid_disk* disk)
 static inline void fs_unlock(struct snapraid_disk* disk)
 {
 #if HAVE_PTHREAD
-	thread_mutex_unlock(&disk->fs_mutex);
+	if (disk->fs_mutex_enabled)
+		thread_mutex_unlock(&disk->fs_mutex);
 #else
 	(void)disk;
 #endif
diff --git a/cmdline/elem.h b/cmdline/elem.h
index 0c4a555a..a29a0b0c 100644
--- a/cmdline/elem.h
+++ b/cmdline/elem.h
@@ -368,6 +368,7 @@ struct snapraid_disk {
 	 * change during multithread processing.
 	 */
 	pthread_mutex_t fs_mutex;
+	int fs_mutex_enabled; /*< If the lock has to be used. */
 #endif
 
 	/**
@@ -968,13 +969,18 @@ static inline tommy_uint32_t dir_name_hash(const char* name)
 /**
  * Allocate a disk.
  */
-struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev, const char* uuid, int skip);
+struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev, const char* uuid, int skip_access);
 
 /**
  * Deallocate a disk.
  */
 void disk_free(struct snapraid_disk* disk);
 
+/**
+ * Enable multithread support for the disk.
+ */
+void disk_start_thread(struct snapraid_disk* disk);
+
 /**
  * Get the size of the disk in blocks.
  */
diff --git a/cmdline/io.c b/cmdline/io.c
index 156d512f..8611002c 100644
--- a/cmdline/io.c
+++ b/cmdline/io.c
@@ -770,6 +770,13 @@ static void io_start_thread(struct snapraid_io* io,
 	int (*block_is_enabled)(void* arg, block_off_t), void* blockarg)
 {
 	unsigned i;
+	tommy_node* j;
+
+	/* enable the filesystem mutex in all disks */
+	for (j = io->state->disklist; j != 0; j = j->next) {
+		struct snapraid_disk* disk = j->data;
+		disk_start_thread(disk);
+	}
 
 	io->block_start = blockstart;
 	io->block_max = blockmax;