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authorZygo Blaxell <ce3g8jdj@umail.furryterror.org>2016-06-12 23:39:58 -0400
committerDavid Sterba <dsterba@suse.com>2016-06-17 18:32:40 +0200
commit90c711ab380d633bf85249bd5d819edb601feda7 (patch)
tree556934ae4488ebae6490610894bbfe92bd405478 /fs
parent3b6571c180da85e43550c608e954ab7b2a31d954 (diff)
btrfs: avoid blocking open_ctree from cleaner_kthread
This fixes a problem introduced in commit 2f3165ecf103599f82bf0ea254039db335fb5005 "btrfs: don't force mounts to wait for cleaner_kthread to delete one or more subvolumes". open_ctree eventually calls btrfs_replay_log which in turn calls btrfs_commit_super which tries to lock the cleaner_mutex, causing a recursive mutex deadlock during mount. Instead of playing whack-a-mole trying to keep up with all the functions that may want to lock cleaner_mutex, put all the cleaner_mutex lockers back where they were, and attack the problem more directly: keep cleaner_kthread asleep until the filesystem is mounted. When filesystems are mounted read-only and later remounted read-write, open_ctree did not set fs_info->open and neither does anything else. Set this flag in btrfs_remount so that neither btrfs_delete_unused_bgs nor cleaner_kthread get confused by the common case of "/" filesystem read-only mount followed by read-write remount. Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/disk-io.c25
-rw-r--r--fs/btrfs/super.c2
2 files changed, 12 insertions, 15 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7b5d5e8efde6..789f5f233940 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1806,6 +1806,13 @@ static int cleaner_kthread(void *arg)
if (btrfs_need_cleaner_sleep(root))
goto sleep;
+ /*
+ * Do not do anything if we might cause open_ctree() to block
+ * before we have finished mounting the filesystem.
+ */
+ if (!root->fs_info->open)
+ goto sleep;
+
if (!mutex_trylock(&root->fs_info->cleaner_mutex))
goto sleep;
@@ -2520,7 +2527,6 @@ int open_ctree(struct super_block *sb,
int num_backups_tried = 0;
int backup_index = 0;
int max_active;
- bool cleaner_mutex_locked = false;
tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
@@ -2999,13 +3005,6 @@ retry_root_backup:
goto fail_sysfs;
}
- /*
- * Hold the cleaner_mutex thread here so that we don't block
- * for a long time on btrfs_recover_relocation. cleaner_kthread
- * will wait for us to finish mounting the filesystem.
- */
- mutex_lock(&fs_info->cleaner_mutex);
- cleaner_mutex_locked = true;
fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
"btrfs-cleaner");
if (IS_ERR(fs_info->cleaner_kthread))
@@ -3065,8 +3064,10 @@ retry_root_backup:
ret = btrfs_cleanup_fs_roots(fs_info);
if (ret)
goto fail_qgroup;
- /* We locked cleaner_mutex before creating cleaner_kthread. */
+
+ mutex_lock(&fs_info->cleaner_mutex);
ret = btrfs_recover_relocation(tree_root);
+ mutex_unlock(&fs_info->cleaner_mutex);
if (ret < 0) {
btrfs_warn(fs_info, "failed to recover relocation: %d",
ret);
@@ -3074,8 +3075,6 @@ retry_root_backup:
goto fail_qgroup;
}
}
- mutex_unlock(&fs_info->cleaner_mutex);
- cleaner_mutex_locked = false;
location.objectid = BTRFS_FS_TREE_OBJECTID;
location.type = BTRFS_ROOT_ITEM_KEY;
@@ -3189,10 +3188,6 @@ fail_cleaner:
filemap_write_and_wait(fs_info->btree_inode->i_mapping);
fail_sysfs:
- if (cleaner_mutex_locked) {
- mutex_unlock(&fs_info->cleaner_mutex);
- cleaner_mutex_locked = false;
- }
btrfs_sysfs_remove_mounted(fs_info);
fail_fsdev_sysfs:
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index bf70d33b5791..60e7179ed4b7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1807,6 +1807,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
}
}
sb->s_flags &= ~MS_RDONLY;
+
+ fs_info->open = 1;
}
out:
wake_up_process(fs_info->transaction_kthread);