On Mon, Oct 03, 2011 at 02:12:41PM -0400, Josef Bacik wrote:
> Some users have requested this and I've found I needed a way to disable cache
> loading without actually clearing the cache, so introduce the no_space_cache
> option. Before we check the super blocks cache generation field and if it was
> populated we always turned space caching on. Now we check this and set the
> space cache option on, and then parse the mount options so that if we want it
> off it get's turned off. Then we check the mount option all the places we do
> the caching work instead of checking the super's cache generation. This makes
> things more consistent and lets us turn space caching off. Thanks,
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> fs/btrfs/extent-tree.c | 9 ++++-----
> fs/btrfs/super.c | 23 ++++++++++++++++++-----
> fs/btrfs/transaction.c | 2 +-
> 3 files changed, 23 insertions(+), 11 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 25b69d0..f9711a8 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -481,7 +481,8 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
> * we likely hold important locks.
> */
> if (trans && (!trans->transaction->in_commit) &&
> - (root && root != root->fs_info->tree_root)) {
> + (root && root != root->fs_info->tree_root) &&
> + btrfs_test_opt(root, SPACE_CACHE)) {
> spin_lock(&cache->lock);
> if (cache->cached != BTRFS_CACHE_NO) {
> spin_unlock(&cache->lock);
> @@ -4223,7 +4224,7 @@ static int update_block_group(struct btrfs_trans_handle *trans,
> spin_lock(&cache->space_info->lock);
> spin_lock(&cache->lock);
>
> - if (btrfs_super_cache_generation(&info->super_copy) != 0 &&
> + if (btrfs_test_opt(root, SPACE_CACHE) &&
> cache->disk_cache_state < BTRFS_DC_CLEAR)
> cache->disk_cache_state = BTRFS_DC_CLEAR;
>
> @@ -7038,13 +7039,11 @@ int btrfs_read_block_groups(struct btrfs_root *root)
> path->reada = 1;
>
> cache_gen = btrfs_super_cache_generation(&root->fs_info->super_copy);
> - if (cache_gen != 0 &&
> + if (btrfs_test_opt(root, SPACE_CACHE) &&
> btrfs_super_generation(&root->fs_info->super_copy) != cache_gen)
> need_clear = 1;
> if (btrfs_test_opt(root, CLEAR_CACHE))
> need_clear = 1;
> - if (!btrfs_test_opt(root, SPACE_CACHE) && cache_gen)
> - printk(KERN_INFO "btrfs: disk space caching is enabled\n");
>
> while (1) {
> ret = find_first_block_group(root, path, &key);
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 934789f..bfee12d 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -164,7 +164,7 @@ enum {
> Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_discard,
> Opt_space_cache, Opt_clear_cache, Opt_user_subvol_rm_allowed,
> Opt_enospc_debug, Opt_subvolrootid, Opt_defrag,
> - Opt_inode_cache, Opt_err,
> + Opt_inode_cache, Opt_no_space_cache, Opt_err,
how about _not_ adding a new optoin and just extend the existing one:
space_cache=off
> };
>
> static match_table_t tokens = {
> @@ -197,6 +197,7 @@ static match_table_t tokens = {
> {Opt_subvolrootid, "subvolrootid=%d"},
> {Opt_defrag, "autodefrag"},
> {Opt_inode_cache, "inode_cache"},
> + {Opt_no_space_cache, "no_space_cache"},
> {Opt_err, NULL},
> };
>
> @@ -208,14 +209,19 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> {
> struct btrfs_fs_info *info = root->fs_info;
> substring_t args[MAX_OPT_ARGS];
> - char *p, *num, *orig;
> + char *p, *num, *orig = NULL;
> + u64 cache_gen;
> int intarg;
> int ret = 0;
> char *compress_type;
> bool compress_force = false;
>
> + cache_gen = btrfs_super_cache_generation(&root->fs_info->super_copy);
> + if (cache_gen)
> + btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +
> if (!options)
> - return 0;
> + goto out;
>
> /*
> * strsep changes the string, duplicate it because parse_options
> @@ -362,9 +368,12 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> btrfs_set_opt(info->mount_opt, DISCARD);
> break;
> case Opt_space_cache:
> - printk(KERN_INFO "btrfs: enabling disk space caching\n");
> btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> break;
> + case Opt_no_space_cache:
> + printk(KERN_INFO "btrfs: disabling disk space caching\n");
> + btrfs_clear_opt(info->mount_opt, SPACE_CACHE);
> + break;
> case Opt_inode_cache:
> printk(KERN_INFO "btrfs: enabling inode map caching\n");
> btrfs_set_opt(info->mount_opt, INODE_MAP_CACHE);
> @@ -393,6 +402,8 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> }
> }
> out:
> + if (!ret && btrfs_test_opt(root, SPACE_CACHE))
> + printk(KERN_INFO "btrfs: disk space caching is enabled\n");
> kfree(orig);
> return ret;
> }
> @@ -686,7 +697,9 @@ static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
> if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
> seq_puts(seq, ",noacl");
> if (btrfs_test_opt(root, SPACE_CACHE))
> - seq_puts(seq, ",space_cache");
> + seq_puts(seq, ",space_cache=on");
> + else
> + seq_puts(seq, ",space_cache=off");
and this is not symmetric to how it's specified to mount, there is no
'no_space_cache' option.
> if (btrfs_test_opt(root, CLEAR_CACHE))
> seq_puts(seq, ",clear_cache");
> if (btrfs_test_opt(root, USER_SUBVOL_RM_ALLOWED))
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 4565579..1e1a481 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -1003,7 +1003,7 @@ static void update_super_roots(struct btrfs_root *root)
> super->root = root_item->bytenr;
> super->generation = root_item->generation;
> super->root_level = root_item->level;
> - if (super->cache_generation != 0 || btrfs_test_opt(root, SPACE_CACHE))
> + if (btrfs_test_opt(root, SPACE_CACHE))
> super->cache_generation = root_item->generation;
> }
otherwise, I agree that this option may come handy, I have seen delayed
mounts when freespace thread was writing out tons of data for ~5-10
minutes during umount.
Same =off extension can be added to inode_cache.
david
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