Commit 94846229 authored by Boris Burkov's avatar Boris Burkov Committed by David Sterba
Browse files

btrfs: keep sb cache_generation consistent with space_cache 



When mounting, btrfs uses the cache_generation in the super block to
determine if space cache v1 is in use. However, by mounting with
nospace_cache or space_cache=v2, it is possible to disable space cache
v1, which does not result in un-setting cache_generation back to 0.

In order to base some logic, like mount option printing in /proc/mounts,
on the current state of the space cache rather than just the values of
the mount option, keep the value of cache_generation consistent with the
status of space cache v1.

We ensure that cache_generation > 0 iff the file system is using
space_cache v1. This requires committing a transaction on any mount
which changes whether we are using v1. (v1->nospace_cache, v1->v2,
nospace_cache->v1, v2->v1).

Since the mechanism for writing out the cache generation is transaction
commit, but we want some finer grained control over when we un-set it,
we can't just rely on the SPACE_CACHE mount option, and introduce an
fs_info flag that mount can use when it wants to unset the generation.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 8b228324

fs/btrfs/ctree.h

+3 −0
Original line number Diff line number Diff line
@@ -559,6 +559,9 @@ enum { 


	/* Indicate that the discard workqueue can service discards. */

	BTRFS_FS_DISCARD_RUNNING,



	/* Indicate that we need to cleanup space cache v1 */

	BTRFS_FS_CLEANUP_SPACE_CACHE_V1,

};



/*

fs/btrfs/disk-io.c

+8 −0
Original line number Diff line number Diff line
@@ -2888,6 +2888,7 @@ void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info) 
int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info)

{

	int ret;

	const bool cache_opt = btrfs_test_opt(fs_info, SPACE_CACHE);

	bool clear_free_space_tree = false;



	if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
@@ -2940,6 +2941,12 @@ int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info) 
		}

	}



	if (cache_opt != btrfs_free_space_cache_v1_active(fs_info)) {

		ret = btrfs_set_free_space_cache_v1_active(fs_info, cache_opt);

		if (ret)

			goto out;

	}



	ret = btrfs_resume_balance_async(fs_info);

	if (ret)

		goto out;
@@ -3410,6 +3417,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device 
			return ret;

		}

	}



	set_bit(BTRFS_FS_OPEN, &fs_info->flags);



clear_oneshot:

fs/btrfs/free-space-cache.c

+28 −0
Original line number Diff line number Diff line
@@ -3763,6 +3763,34 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group, 
	return ret;

}



bool btrfs_free_space_cache_v1_active(struct btrfs_fs_info *fs_info)

{

	return btrfs_super_cache_generation(fs_info->super_copy);

}



int btrfs_set_free_space_cache_v1_active(struct btrfs_fs_info *fs_info, bool active)

{

	struct btrfs_trans_handle *trans;

	int ret;



	/*

	 * update_super_roots will appropriately set

	 * super_copy->cache_generation based on the SPACE_CACHE option, so all

	 * we have to do is trigger a transaction commit.

	 */

	trans = btrfs_start_transaction(fs_info->tree_root, 0);

	if (IS_ERR(trans))

		return PTR_ERR(trans);



	if (!active)

		set_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags);



	ret = btrfs_commit_transaction(trans);

	clear_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags);



	return ret;

}



#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS

/*

 * Use this if you need to make a bitmap or extent entry specifically, it

fs/btrfs/free-space-cache.h

+2 −0
Original line number Diff line number Diff line
@@ -135,6 +135,8 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group, 
				   u64 *trimmed, u64 start, u64 end, u64 minlen,

				   u64 maxlen, bool async);



bool btrfs_free_space_cache_v1_active(struct btrfs_fs_info *fs_info);

int btrfs_set_free_space_cache_v1_active(struct btrfs_fs_info *fs_info, bool active);

/* Support functions for running our sanity tests */

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS

int test_add_free_space_entry(struct btrfs_block_group *cache,

fs/btrfs/super.c

+7 −3
Original line number Diff line number Diff line
@@ -552,7 +552,6 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options, 
{

	substring_t args[MAX_OPT_ARGS];

	char *p, *num;

	u64 cache_gen;

	int intarg;

	int ret = 0;

	char *compress_type;
@@ -562,10 +561,9 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options, 
	bool saved_compress_force;

	int no_compress = 0;



	cache_gen = btrfs_super_cache_generation(info->super_copy);

	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))

		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);

	else if (cache_gen) {

	else if (btrfs_free_space_cache_v1_active(info)) {

		if (btrfs_is_zoned(info)) {

			btrfs_info(info,

			"zoned: clearing existing space cache");
@@ -1864,6 +1862,8 @@ static inline void btrfs_remount_begin(struct btrfs_fs_info *fs_info, 
static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,

					 unsigned long old_opts)

{

	const bool cache_opt = btrfs_test_opt(fs_info, SPACE_CACHE);



	/*

	 * We need to cleanup all defragable inodes if the autodefragment is

	 * close or the filesystem is read only.
@@ -1880,6 +1880,10 @@ static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info, 
	else if (btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&

		 !btrfs_test_opt(fs_info, DISCARD_ASYNC))

		btrfs_discard_cleanup(fs_info);



	/* If we toggled space cache */

	if (cache_opt != btrfs_free_space_cache_v1_active(fs_info))

		btrfs_set_free_space_cache_v1_active(fs_info, cache_opt);

}



static int btrfs_remount(struct super_block *sb, int *flags, char *data)