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btrfs: defer adding raid type kobject until after chunk relocation

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Any time the first block group of a new type is created, we add a new
kobject to sysfs to hold the attributes for that type.  Kobject-internal
allocations always use GFP_KERNEL, making them prone to fs-reclaim races.
While it appears as if this can occur any time a block group is created,
the only times the first block group of a new type can be created in
memory is at mount and when we create the first new block group during
raid conversion.

This patch adds a new list to track pending kobject additions and then
handles them after we do chunk relocation.  Between relocating the
target chunk (or forcing allocation of a new chunk in the case of data)
and removing the old chunk, we're in a safe place for fs-reclaim to
occur.  We're holding the volume mutex, which is already held across
page faults, and the delete_unused_bgs_mutex, which will only stall
the cleaner thread.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Jeff Mahoney
2018-03-20 15:25:26 -04:00
committed by David Sterba
parent dc2d3005d2
commit 75cb379d26
5 changed files with 62 additions and 20 deletions
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6
fs/btrfs/ctree.h
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@@ -385,8 +385,9 @@ struct btrfs_dev_replace {
/* For raid type sysfs entries */
struct raid_kobject {
int raid_type;
u64 flags;
struct kobject kobj;
struct list_head list;
};
struct btrfs_space_info {
@@ -940,6 +941,8 @@ struct btrfs_fs_info {
u32 thread_pool_size;
struct kobject *space_info_kobj;
struct list_head pending_raid_kobjs;
spinlock_t pending_raid_kobjs_lock; /* uncontended */
u64 total_pinned;
@@ -2700,6 +2703,7 @@ int btrfs_can_relocate(struct btrfs_fs_info *fs_info, u64 bytenr);
int btrfs_make_block_group(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytes_used,
u64 type, u64 chunk_offset, u64 size);
void btrfs_add_raid_kobjects(struct btrfs_fs_info *fs_info);
struct btrfs_trans_handle *btrfs_start_trans_remove_block_group(
struct btrfs_fs_info *fs_info,
const u64 chunk_offset);