Attachment 55990 Details for Bug 130693

[patch] Kernel patch to start md arrays read-only

001MdStartRO (text/plain), 4.44 KB, created by Neil Brown on 2005-10-31 04:23:17 UTC

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Creator: Neil Brown

Created: 2005-10-31 04:23:17 UTC

Size: 4.44 KB

patch

obsolete

>Status: ok
>
>Allow md arrays to be started read-only (module parameter).
>
>When an md array is started, the superblock will be written,
>and resync may commense.  This is not good if you want to be
>completely read-only as, for example, when preparing to resume
>from a suspend-to-disk image.
>
>So introduce a module parameter "start_ro" which can be set
>to '1' at boot, at module load, or via 
>  /sys/module/md_mod/parameters/start_ro
>
>When this is set, new arrays get an 'auto-ro' mode, which disables all
>internal io (superblock updates, resync, recovery) and is automatically
>switched to 'rw' when the first write request arrives.
>
>The array can be set to true 'ro' mode using 'mdadm -r' before
>the first write request, or resync can be started without a
>write using 'mdadm -w'.
>
>Signed-off-by: Neil Brown <neilb@suse.de>
>
>### Diffstat output
> ./drivers/md/md.c |   59 ++++++++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 51 insertions(+), 8 deletions(-)
>
>diff ./drivers/md/md.c~current~ ./drivers/md/md.c
>--- ./drivers/md/md.c~current~	2005-10-31 12:19:53.000000000 +1100
>+++ ./drivers/md/md.c	2005-10-31 15:15:39.000000000 +1100
>@@ -131,6 +131,8 @@ static ctl_table raid_root_table[] = {
> 
> static struct block_device_operations md_fops;
> 
>+static int start_readonly;
>+
> /*
>  * Enables to iterate over all existing md arrays
>  * all_mddevs_lock protects this list.
>@@ -2057,6 +2059,9 @@ static int do_md_run(mddev_t * mddev)
> 	mddev->resync_max_sectors = mddev->size << 1; /* may be over-ridden by personality */
> 	mddev->barriers_work = 1;
> 
>+	if (start_readonly)
>+		mddev->ro = 2; /* read-only, but switch on first write */
>+
> 	/* before we start the array running, initialise the bitmap */
> 	err = bitmap_create(mddev);
> 	if (err)
>@@ -2169,7 +2174,7 @@ static int do_md_stop(mddev_t * mddev, i
> 
> 		if (ro) {
> 			err  = -ENXIO;
>-			if (mddev->ro)
>+			if (mddev->ro==1)
> 				goto out;
> 			mddev->ro = 1;
> 		} else {
>@@ -3286,12 +3291,22 @@ static int md_ioctl(struct inode *inode,
> 
> 	/*
> 	 * The remaining ioctls are changing the state of the
>-	 * superblock, so we do not allow read-only arrays
>-	 * here:
>+	 * superblock, so we do not allow them on read-only arrays.
>+	 * However non-MD ioctls (e.g. get-size) will still come through
>+	 * here and hit the 'default' below, so only disallow
>+	 * 'md' ioctls, and switch to rw mode if started auto-readonly.
> 	 */
>-	if (mddev->ro) {
>-		err = -EROFS;
>-		goto abort_unlock;
>+	if (_IOC_TYPE(cmd) == MD_MAJOR &&
>+	    mddev->ro && mddev->pers) {
>+		if (mddev->ro == 2) {
>+			mddev->ro = 0;
>+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
>+		md_wakeup_thread(mddev->thread);
>+
>+		} else {
>+			err = -EROFS;
>+			goto abort_unlock;
>+		}
> 	}
> 
> 	switch (cmd)
>@@ -3678,8 +3693,10 @@ static int md_seq_show(struct seq_file *
> 		seq_printf(seq, "%s : %sactive", mdname(mddev),
> 						mddev->pers ? "" : "in");
> 		if (mddev->pers) {
>-			if (mddev->ro)
>+			if (mddev->ro==1)
> 				seq_printf(seq, " (read-only)");
>+			if (mddev->ro==2)
>+				seq_printf(seq, "(auto-read-only)");
> 			seq_printf(seq, " %s", mddev->pers->name);
> 		}
> 
>@@ -3723,7 +3740,9 @@ static int md_seq_show(struct seq_file *
> 				status_resync (seq, mddev);
> 				seq_printf(seq, "\n      ");
> 			} else if (mddev->curr_resync == 1 || mddev->curr_resync == 2)
>-				seq_printf(seq, "	resync=DELAYED\n      ");
>+				seq_printf(seq, "\tresync=DELAYED\n      ");
>+			else if (mddev->recovery_cp < MaxSector)
>+				seq_printf(seq, "\tresync=PENDING\n      ");
> 		} else
> 			seq_printf(seq, "\n       ");
> 
>@@ -3860,6 +3879,13 @@ void md_write_start(mddev_t *mddev, stru
> 	if (bio_data_dir(bi) != WRITE)
> 		return;
> 
>+	BUG_ON(mddev->ro == 1);
>+	if (mddev->ro == 2) {
>+		/* need to switch to read/write */
>+		mddev->ro = 0;
>+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
>+		md_wakeup_thread(mddev->thread);
>+	}
> 	atomic_inc(&mddev->writes_pending);
> 	if (mddev->in_sync) {
> 		spin_lock_irq(&mddev->write_lock);
>@@ -4455,6 +4481,23 @@ static __exit void md_exit(void)
> module_init(md_init)
> module_exit(md_exit)
> 
>+static int get_ro(char *buffer, struct kernel_param *kp)
>+{
>+	return sprintf(buffer, "%d", start_readonly);
>+}
>+static int set_ro(const char *val, struct kernel_param *kp)
>+{
>+	char *e;
>+	int num = simple_strtoul(val, &e, 10);
>+	if (*val && (*e == '\0' || *e == '\n')) {
>+		start_readonly = num;
>+		return 0;;
>+	}
>+	return -EINVAL;
>+}
>+
>+module_param_call(start_ro, set_ro, get_ro, NULL, 0600);
>+
> EXPORT_SYMBOL(register_md_personality);
> EXPORT_SYMBOL(unregister_md_personality);
> EXPORT_SYMBOL(md_error);

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Attachments on bug 130693: 55486 | 55487 | 55644 | 55990 | 55991