diff options
Diffstat (limited to 'libdiskfs')
| -rw-r--r-- | libdiskfs/diskfs.h | 45 |
1 files changed, 41 insertions, 4 deletions
diff --git a/libdiskfs/diskfs.h b/libdiskfs/diskfs.h index 1d24661d..866083f0 100644 --- a/libdiskfs/diskfs.h +++ b/libdiskfs/diskfs.h @@ -532,17 +532,39 @@ diskfs_nref (struct node *np) extern inline void diskfs_nput (struct node *np) { + int tried_drop_softrefs = 0; + + loop: spin_lock (&diskfs_node_refcnt_lock); assert (np->references); np->references--; if (np->references + np->light_references == 0) diskfs_drop_node (np); - else if (np->references == 0) + else if (np->references == 0 && !tried_drop_softrefs) { spin_unlock (&diskfs_node_refcnt_lock); diskfs_lost_hardrefs (np); if (!np->dn_stat.st_nlink) - diskfs_try_dropping_softrefs (np); + { + /* There are no links. If there are soft references that + can be dropped, we can't let them postpone deallocation. + So attempt to drop them. But that's a user-supplied + routine, which might result in further recursive calls to + the ref-counting system. So we have to reacquire our + reference around the call to forestall disaster. */ + spin_unlock (&diskfs_node_refcnt_lock); + np->references++; + spin_unlock (&diskfs_node_refcnt_lock); + + diskfs_try_dropping_softrefs (np); + + /* But there's no value in looping forever in this + routine; only try to drop soft refs once. */ + tried_drop_softrefs = 1; + + /* Now we can drop the reference back... */ + goto loop; + } } else spin_unlock (&diskfs_node_refcnt_lock); @@ -557,6 +579,9 @@ diskfs_nput (struct node *np) extern inline void diskfs_nrele (struct node *np) { + int tried_drop_softrefs = 0; + + loop: spin_lock (&diskfs_node_refcnt_lock); assert (np->references); np->references--; @@ -570,8 +595,20 @@ diskfs_nrele (struct node *np) mutex_lock (&np->lock); spin_unlock (&diskfs_node_refcnt_lock); diskfs_lost_hardrefs (np); - if (!np->dn_stat.st_nlink) - diskfs_try_dropping_softrefs (np); + if (!np->dn_stat.st_nlink && !tried_drop_softrefs) + { + /* Same issue here as in nput; see that for explanation */ + spin_unlock (&diskfs_node_refcnt_lock); + np->references++; + spin_unlock (&diskfs_node_refcnt_lock); + + diskfs_try_dropping_softrefs (np); + tried_drop_softrefs = 1; + + /* Now we can drop the reference back... */ + mutex_unlock (&np->lock); + goto loop; + } mutex_unlock (&np->lock); } else |