Re: [PATCH] Btrfs: make filesystem read-only when submitting barrier fails

)sorry, forgot to CC btrfs Maillist)

On 08/11/2012 10:36 AM, Liu Bo wrote:

On 08/10/2012 09:38 PM, Stefan Behrens wrote:

quoted

So far the return code of barrier_all_devices() is ignored, which
means that errors are ignored. The result can be a corrupt
filesystem which is not consistent.
This commit adds code to evaluate the return code of
barrier_all_devices(). The normal btrfs_error() mechanism is used to
switch the filesystem into read-only mode when errors are detected.

In order to decide whether barrier_all_devices() should return
error or success, the number of disks that are allowed to fail the
barrier submission is calculated. This calculation accounts for the
worst RAID level of metadata, system and data. If single, dup or
RAID0 is in use, a single disk error is already considered to be
fatal. Otherwise a single disk error is tolerated.

The calculation of the number of disks that are tolerated to fail
the barrier operation is performed when the filesystem gets mounted,
when a balance operation is started and finished, and when devices
are added or removed.

Signed-off-by: Stefan Behrens <redacted>
---
 fs/btrfs/ctree.h    |   5 +++
 fs/btrfs/disk-io.c  | 109 +++++++++++++++++++++++++++++++++++++++++++++-------
 fs/btrfs/disk-io.h  |   2 +
 fs/btrfs/ioctl.c    |   8 ++--
 fs/btrfs/tree-log.c |   7 +++-
 fs/btrfs/volumes.c  |  30 +++++++++++++++
 6 files changed, 142 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index adb1cd7..af38d6d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h

@@ -1442,6 +1442,8 @@ struct btrfs_fs_info {
 
 	/* next backup root to be overwritten */
 	int backup_root_index;
+
+	int num_tolerated_disk_barrier_failures;

[...]  

quoted

+int btrfs_calc_num_tolerated_disk_barrier_failures(
+	struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_ioctl_space_info space;
+	struct btrfs_space_info *sinfo;
+	u64 types[] = {BTRFS_BLOCK_GROUP_DATA,
+		       BTRFS_BLOCK_GROUP_SYSTEM,
+		       BTRFS_BLOCK_GROUP_METADATA,
+		       BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA};
+	int num_types = 4;
+	int i;
+	int c;
+	int num_tolerated_disk_barrier_failures =
+		(int)fs_info->fs_devices->num_devices;
+
+	for (i = 0; i < num_types; i++) {
+		struct btrfs_space_info *tmp;
+
+		sinfo = NULL;
+		rcu_read_lock();
+		list_for_each_entry_rcu(tmp, &fs_info->space_info, list) {
+			if (tmp->flags == types[i]) {
+				sinfo = tmp;
+				break;
+			}
+		}
+		rcu_read_unlock();
+
+		if (!sinfo)
+			continue;
+
+		down_read(&sinfo->groups_sem);
+		for (c = 0; c < BTRFS_NR_RAID_TYPES; c++) {
+			if (!list_empty(&sinfo->block_groups[c])) {
+				u64 flags;
+
+				btrfs_get_block_group_info(
+					&sinfo->block_groups[c], &space);
+				if (space.total_bytes == 0 ||
+				    space.used_bytes == 0)
+					continue;
+				flags = space.flags;
+				/*
+				 * return
+				 * 0: if dup, single or RAID0 is configured for
+				 *    any of metadata, system or data, else
+				 * 1: if RAID5 is configured, or if RAID1 or
+				 *    RAID10 is configured and only two mirrors
+				 *    are used, else
+				 * 2: if RAID6 is configured, else
+				 * num_mirrors - 1: if RAID1 or RAID10 is
+				 *                  configured and more than
+				 *                  2 mirrors are used.
+				 */
+				if (num_tolerated_disk_barrier_failures > 0 &&
+				    ((flags & (BTRFS_BLOCK_GROUP_DUP |
+					       BTRFS_BLOCK_GROUP_RAID0)) ||
+				     ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK)
+				      == 0)))

Good work.

We already have __get_block_group_index(), for dup, single, raid0 we can do the same thing like
this:
__get_block_group_index(flags) > 1

the only problem is to make the function public :)

quoted

+					num_tolerated_disk_barrier_failures = 0;
+				else if (num_tolerated_disk_barrier_failures > 1
+					 &&
+					 (flags & (BTRFS_BLOCK_GROUP_RAID1 |
+						   BTRFS_BLOCK_GROUP_RAID10)))
+					num_tolerated_disk_barrier_failures = 1;
+			}
+		}
+		up_read(&sinfo->groups_sem);
+	}
+
+	return num_tolerated_disk_barrier_failures;
+}
+
 int write_all_supers(struct btrfs_root *root, int max_mirrors)
 {
 	struct list_head *head;

@@ -2979,8 +3054,16 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors)
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
 	head = &root->fs_info->fs_devices->devices;
 
-	if (do_barriers)
-		barrier_all_devices(root->fs_info);
+	if (do_barriers) {
+		ret = barrier_all_devices(root->fs_info);
+		if (ret) {
+			mutex_unlock(
+				&root->fs_info->fs_devices->device_list_mutex);
+			btrfs_error(root->fs_info, ret,
+				    "errors while submitting device barriers.");
+			return ret;
+		}
+	}
 
 	list_for_each_entry_rcu(dev, head, dev_list) {
 		if (!dev->bdev) {

diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index c5b00a7..2025a91 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h

@@ -95,6 +95,8 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
 				     u64 objectid);
 int btree_lock_page_hook(struct page *page, void *data,
 				void (*flush_fn)(void *));
+int btrfs_calc_num_tolerated_disk_barrier_failures(
+	struct btrfs_fs_info *fs_info);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void btrfs_init_lockdep(void);

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 43f0012..6cd4125 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c

@@ -2852,8 +2852,8 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 	return 0;
 }
 
-static void get_block_group_info(struct list_head *groups_list,
-				 struct btrfs_ioctl_space_info *space)
+void btrfs_get_block_group_info(struct list_head *groups_list,
+				struct btrfs_ioctl_space_info *space)
 {
 	struct btrfs_block_group_cache *block_group;
 

@@ -2961,8 +2961,8 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
 		down_read(&info->groups_sem);
 		for (c = 0; c < BTRFS_NR_RAID_TYPES; c++) {
 			if (!list_empty(&info->block_groups[c])) {
-				get_block_group_info(&info->block_groups[c],
-						     &space);
+				btrfs_get_block_group_info(
+					&info->block_groups[c], &space);
 				memcpy(dest, &space, sizeof(space));
 				dest++;
 				space_args.total_spaces++;

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index c86670f..c30e1c0 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c

@@ -2171,9 +2171,12 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	 * in and cause problems either.
 	 */
 	btrfs_scrub_pause_super(root);
-	write_ctree_super(trans, root->fs_info->tree_root, 1);
+	ret = write_ctree_super(trans, root->fs_info->tree_root, 1);
 	btrfs_scrub_continue_super(root);
-	ret = 0;
+	if (ret) {
+		btrfs_abort_transaction(trans, root, ret);
+		goto out_wake_log_root;
+	}
 
 	mutex_lock(&root->log_mutex);
 	if (root->last_log_commit < log_transid)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b8708f9..48ccaa4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c

@@ -1474,6 +1474,9 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 		free_fs_devices(cur_devices);
 	}
 
+	root->fs_info->num_tolerated_disk_barrier_failures =
+		btrfs_calc_num_tolerated_disk_barrier_failures(root->fs_info);
+
 	/*
 	 * at this point, the device is zero sized.  We want to
 	 * remove it from the devices list and zero out the old super

@@ -1796,6 +1799,8 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	btrfs_clear_space_info_full(root->fs_info);
 
 	unlock_chunks(root);
+	root->fs_info->num_tolerated_disk_barrier_failures =
+		btrfs_calc_num_tolerated_disk_barrier_failures(root->fs_info);
 	ret = btrfs_commit_transaction(trans, root);
 
 	if (seeding_dev) {

@@ -2807,6 +2812,26 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
 		}
 	}
 
+	if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) {
+		int num_tolerated_disk_barrier_failures;
+		u64 target = bctl->sys.target;
+
+		num_tolerated_disk_barrier_failures =
+			btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);
+		if (num_tolerated_disk_barrier_failures > 0 &&
+		    (target &
+		     (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID0 |
+		      BTRFS_AVAIL_ALLOC_BIT_SINGLE)))

ditto.

thanks,
liubo

quoted

+			num_tolerated_disk_barrier_failures = 0;
+		else if (num_tolerated_disk_barrier_failures > 1 &&
+			 (target &
+			  (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10)))
+			num_tolerated_disk_barrier_failures = 1;
+
+		fs_info->num_tolerated_disk_barrier_failures =
+			num_tolerated_disk_barrier_failures;
+	}
+
 	ret = insert_balance_item(fs_info->tree_root, bctl);
 	if (ret && ret != -EEXIST)
 		goto out;

@@ -2839,6 +2864,11 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
 		__cancel_balance(fs_info);
 	}
 
+	if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) {
+		fs_info->num_tolerated_disk_barrier_failures =
+			btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);
+	}
+
 	wake_up(&fs_info->balance_wait_q);
 
 	return ret;