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Btrfs: add missing spin_lock for insertion into tree mod log

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tree_mod_alloc calls __get_tree_mod_seq and must acquire a spinlock before
doing so.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
This commit is contained in:
Jan Schmidt 2012-05-31 14:00:15 +02:00
parent 3301958b7c
commit 926dd8a640
1 changed files with 18 additions and 5 deletions
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23
fs/btrfs/ctree.c
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@ -455,11 +455,11 @@ __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
return ret; return ret;
} }
int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags, static inline int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
struct tree_mod_elem **tm_ret) struct tree_mod_elem **tm_ret)
{ {
struct tree_mod_elem *tm; struct tree_mod_elem *tm;
u64 seq = 0; int seq;
smp_mb(); smp_mb();
if (list_empty(&fs_info->tree_mod_seq_list)) if (list_empty(&fs_info->tree_mod_seq_list))
@ -469,9 +469,22 @@ int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
if (!tm) if (!tm)
return -ENOMEM; return -ENOMEM;
__get_tree_mod_seq(fs_info, &tm->elem);
seq = tm->elem.seq;
tm->elem.flags = 0; tm->elem.flags = 0;
spin_lock(&fs_info->tree_mod_seq_lock);
if (list_empty(&fs_info->tree_mod_seq_list)) {
/*
* someone emptied the list while we were waiting for the lock.
* we must not add to the list, because no blocker exists. items
* are removed from the list only when the existing blocker is
* removed from the list.
*/
kfree(tm);
seq = 0;
} else {
__get_tree_mod_seq(fs_info, &tm->elem);
seq = tm->elem.seq;
}
spin_unlock(&fs_info->tree_mod_seq_lock);
return seq; return seq;
} }