File 0026-mdmon-already-read-sysfs-files-once-after-opening.patch of Package mdadm.5365

From da5a36fa1f0ae8c47075d696d14309c74fd350dc Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Wed, 17 Sep 2014 15:02:18 +1000
Subject: [PATCH 036/359] mdmon: already read sysfs files once after opening.
References: bsc#1081910

seq_file in the kernel will allocate a read buffer on
first read.  We want this to happen under the managemon thread,
not the 'monitor' thread, as the latter is not allow to allocate
memory (might deadlock).
So do a first read after opening.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Coly Li <colyli@suse.de>

---
 managemon.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/managemon.c b/managemon.c
index 1c9eccc..9b14d1e 100644
--- a/managemon.c
+++ b/managemon.c
@@ -402,6 +402,20 @@ static void manage_container(struct mdstat_ent *mdstat,
 	}
 }
 
+static int sysfs_open2(char *devnum, char *name, char *attr)
+{
+	int fd = sysfs_open(devnum, name, attr);
+	if (fd >= 0) {
+		/* seq_file in the kernel allocates buffer space
+		 * on the first read.  Do that now so 'monitor'
+		 * never needs too.
+		 */
+		char buf[200];
+		read(fd, buf, sizeof(buf));
+	}
+	return fd;
+}
+
 static int disk_init_and_add(struct mdinfo *disk, struct mdinfo *clone,
 			     struct active_array *aa)
 {
@@ -409,10 +423,11 @@ static int disk_init_and_add(struct mdinfo *disk, struct mdinfo *clone,
 		return -1;
 
 	*disk = *clone;
-	disk->recovery_fd = sysfs_open(aa->info.sys_name, disk->sys_name, "recovery_start");
+	disk->recovery_fd = sysfs_open2(aa->info.sys_name, disk->sys_name,
+					"recovery_start");
 	if (disk->recovery_fd < 0)
 		return -1;
-	disk->state_fd = sysfs_open(aa->info.sys_name, disk->sys_name, "state");
+	disk->state_fd = sysfs_open2(aa->info.sys_name, disk->sys_name, "state");
 	if (disk->state_fd < 0) {
 		close(disk->recovery_fd);
 		return -1;
@@ -692,11 +707,12 @@ static void manage_new(struct mdstat_ent *mdstat,
 		}
 	}
 
-	new->action_fd = sysfs_open(new->info.sys_name, NULL, "sync_action");
-	new->info.state_fd = sysfs_open(new->info.sys_name, NULL, "array_state");
-	new->resync_start_fd = sysfs_open(new->info.sys_name, NULL, "resync_start");
-	new->metadata_fd = sysfs_open(new->info.sys_name, NULL, "metadata_version");
-	new->sync_completed_fd = sysfs_open(new->info.sys_name, NULL, "sync_completed");
+	new->action_fd = sysfs_open2(new->info.sys_name, NULL, "sync_action");
+	new->info.state_fd = sysfs_open2(new->info.sys_name, NULL, "array_state");
+	new->resync_start_fd = sysfs_open2(new->info.sys_name, NULL, "resync_start");
+	new->metadata_fd = sysfs_open2(new->info.sys_name, NULL, "metadata_version");
+	new->sync_completed_fd = sysfs_open2(new->info.sys_name, NULL, "sync_completed");
+
 	dprintf("%s: inst: %s action: %d state: %d\n", __func__, inst,
 		new->action_fd, new->info.state_fd);
 
-- 
2.16.1