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btrfs: keep sb cache_generation consistent with space_cache

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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: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Boris Burkov 2020-11-18 15:06:22 -08:00 committed by David Sterba
parent 8b228324a8
commit 9484622945
6 changed files with 50 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/btrfs/ctree.h
View File

@ -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,
};
/*

8
fs/btrfs/disk-io.c
View File

@ -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:

28
fs/btrfs/free-space-cache.c
View File

@ -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

2
fs/btrfs/free-space-cache.h
View File

@ -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,

10
fs/btrfs/super.c
View File

@ -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)

2
fs/btrfs/transaction.c
View File

@ -1796,6 +1796,8 @@ static void update_super_roots(struct btrfs_fs_info *fs_info)
super->root_level = root_item->level;
if (btrfs_test_opt(fs_info, SPACE_CACHE))
super->cache_generation = root_item->generation;
else if (test_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags))
super->cache_generation = 0;
if (test_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags))
super->uuid_tree_generation = root_item->generation;
}