add patch series

1 files changed, 207 insertions, 0 deletions

diff --git a/debian/patches/0003-ext2fs-use-a-seperate-lock-to-protect-nodehash.patch b/debian/patches/0003-ext2fs-use-a-seperate-lock-to-protect-nodehash.patch
new file mode 100644
index 00000000..e2553b40
--- /dev/null
+++ b/debian/patches/0003-ext2fs-use-a-seperate-lock-to-protect-nodehash.patch
@@ -0,0 +1,207 @@
+From a0ce1cfd7c411ac909ce7fa49048b45dcab41758 Mon Sep 17 00:00:00 2001
+From: Justus Winter <4winter@informatik.uni-hamburg.de>
+Date: Tue, 13 May 2014 13:09:15 +0200
+Subject: [PATCH 3/6] ext2fs: use a seperate lock to protect nodehash
+
+Previously, ext2fs used diskfs_node_refcnt_lock to serialize access to
+the nodehash.
+
+Use a separate lock to protect nodehash.  Adjust the reference
+counting accordingly.  Every node in the nodehash carries a light
+reference.  When we are asked to give up that light reference, we
+reacquire our lock momentarily to check whether someone else
+reacquired a reference through the nodehash.
+
+* ext2fs/inode.c (nodecache_lock): New lock.
+(diskfs_cached_lookup): Use a separate lock to protect nodehash.
+Adjust the reference counting accordingly.
+(ifind): Likewise.
+(diskfs_node_iterate): Likewise.
+(diskfs_node_norefs): Move the code removing the node from nodehash...
+(diskfs_try_dropping_softrefs): ... here, where we check whether
+someone reacquired a reference, and if so hold on to our light
+reference.
+---
+ ext2fs/inode.c | 80 ++++++++++++++++++++++++++++++++++++++++++----------------
+ 1 file changed, 58 insertions(+), 22 deletions(-)
+
+diff --git a/ext2fs/inode.c b/ext2fs/inode.c
+index ed78265..6e46f2b 100644
+--- a/ext2fs/inode.c
++++ b/ext2fs/inode.c
+@@ -46,8 +46,18 @@
+ #define	INOHASH(ino)	(((unsigned)(ino))%INOHSZ)
+ #endif
+ 
++/* The nodehash is a cache of nodes.
++
++   Access to nodehash and nodehash_nr_items is protected by
++   nodecache_lock.
++
++   Every node in the nodehash carries a light reference.  When we are
++   asked to give up that light reference, we reacquire our lock
++   momentarily to check whether someone else reacquired a reference
++   through the nodehash.  */
+ static struct node *nodehash[INOHSZ];
+ static size_t nodehash_nr_items;
++static pthread_rwlock_t nodecache_lock = PTHREAD_RWLOCK_INITIALIZER;
+ 
+ static error_t read_node (struct node *np);
+ 
+@@ -71,24 +81,22 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
+   struct node *np;
+   struct disknode *dn;
+ 
+-  pthread_spin_lock (&diskfs_node_refcnt_lock);
++  pthread_rwlock_rdlock (&nodecache_lock);
+   for (np = nodehash[INOHASH(inum)]; np; np = np->dn->hnext)
+     if (np->cache_id == inum)
+       {
+-	np->references++;
+-	pthread_spin_unlock (&diskfs_node_refcnt_lock);
++	diskfs_nref (np);
++	pthread_rwlock_unlock (&nodecache_lock);
+ 	pthread_mutex_lock (&np->lock);
+ 	*npp = np;
+ 	return 0;
+       }
++  pthread_rwlock_unlock (&nodecache_lock);
+ 
+   /* Format specific data for the new node.  */
+   dn = malloc (sizeof (struct disknode));
+   if (! dn)
+-    {
+-      pthread_spin_unlock (&diskfs_node_refcnt_lock);
+-      return ENOMEM;
+-    }
++    return ENOMEM;
+   dn->dirents = 0;
+   dn->dir_idx = 0;
+   dn->pager = 0;
+@@ -102,14 +110,15 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
+   pthread_mutex_lock (&np->lock);
+ 
+   /* Put NP in NODEHASH.  */
++  pthread_rwlock_wrlock (&nodecache_lock);
+   dn->hnext = nodehash[INOHASH(inum)];
+   if (dn->hnext)
+     dn->hnext->dn->hprevp = &dn->hnext;
+   dn->hprevp = &nodehash[INOHASH(inum)];
+   nodehash[INOHASH(inum)] = np;
++  diskfs_nref_light (np);
+   nodehash_nr_items += 1;
+-
+-  pthread_spin_unlock (&diskfs_node_refcnt_lock);
++  pthread_rwlock_unlock (&nodecache_lock);
+ 
+   /* Get the contents of NP off disk.  */
+   err = read_node (np);
+@@ -140,14 +149,13 @@ ifind (ino_t inum)
+ {
+   struct node *np;
+ 
+-  pthread_spin_lock (&diskfs_node_refcnt_lock);
++  pthread_rwlock_rdlock (&nodecache_lock);
+   for (np = nodehash[INOHASH(inum)]; np; np = np->dn->hnext)
+     {
+       if (np->cache_id != inum)
+ 	continue;
+ 
+-      assert (np->references);
+-      pthread_spin_unlock (&diskfs_node_refcnt_lock);
++      pthread_rwlock_unlock (&nodecache_lock);
+       return np;
+     }
+   assert (0);
+@@ -158,11 +166,6 @@ ifind (ino_t inum)
+ void
+ diskfs_node_norefs (struct node *np)
+ {
+-  *np->dn->hprevp = np->dn->hnext;
+-  if (np->dn->hnext)
+-    np->dn->hnext->dn->hprevp = np->dn->hprevp;
+-  nodehash_nr_items -= 1;
+-
+   if (np->dn->dirents)
+     free (np->dn->dirents);
+   assert (!np->dn->pager);
+@@ -180,6 +183,35 @@ diskfs_node_norefs (struct node *np)
+ void
+ diskfs_try_dropping_softrefs (struct node *np)
+ {
++  pthread_rwlock_wrlock (&nodecache_lock);
++  if (np->dn->hnext != NULL)
++    {
++      /* Check if someone reacquired a reference through the
++         nodehash.  */
++      unsigned int references;
++      pthread_spin_lock (&diskfs_node_refcnt_lock);
++      references = np->references;
++      pthread_spin_unlock (&diskfs_node_refcnt_lock);
++
++      /* An additional reference is acquired by libdiskfs across calls
++         to diskfs_try_dropping_softrefs.  */
++      if (references > 1)
++        {
++          /* A reference was reacquired through a hash table lookup.
++             It's fine, we didn't touch anything yet. */
++          pthread_rwlock_unlock (&nodecache_lock);
++          return;
++        }
++
++      *np->dn->hprevp = np->dn->hnext;
++      if (np->dn->hnext)
++        np->dn->hnext->dn->hprevp = np->dn->hprevp;
++      np->dn->hnext = NULL;
++      nodehash_nr_items -= 1;
++      diskfs_nrele_light (np);
++    }
++  pthread_rwlock_unlock (&nodecache_lock);
++
+   drop_pager_softrefs (np);
+ }
+ 
+@@ -556,12 +588,12 @@ diskfs_node_iterate (error_t (*fun)(struct node *))
+   size_t num_nodes;
+   struct node *node, **node_list, **p;
+ 
+-  pthread_spin_lock (&diskfs_node_refcnt_lock);
++  pthread_rwlock_rdlock (&nodecache_lock);
+ 
+   /* We must copy everything from the hash table into another data structure
+      to avoid running into any problems with the hash-table being modified
+      during processing (normally we delegate access to hash-table with
+-     diskfs_node_refcnt_lock, but we can't hold this while locking the
++     nodecache_lock, but we can't hold this while locking the
+      individual node locks).  */
+   num_nodes = nodehash_nr_items;
+ 
+@@ -570,7 +602,7 @@ diskfs_node_iterate (error_t (*fun)(struct node *))
+   node_list = malloc (num_nodes * sizeof (struct node *));
+   if (node_list == NULL)
+     {
+-      pthread_spin_unlock (&diskfs_node_refcnt_lock);
++      pthread_rwlock_unlock (&nodecache_lock);
+       ext2_debug ("unable to allocate temporary node table");
+       return ENOMEM;
+     }
+@@ -580,10 +612,14 @@ diskfs_node_iterate (error_t (*fun)(struct node *))
+     for (node = nodehash[n]; node; node = node->dn->hnext)
+       {
+ 	*p++ = node;
+-	node->references++;
++
++        /* We acquire a hard reference for node, but without using
++           diskfs_nref.  We do this so that diskfs_new_hardrefs will not
++           get called.  */
++        node->references++;
+       }
+ 
+-  pthread_spin_unlock (&diskfs_node_refcnt_lock);
++  pthread_rwlock_unlock (&nodecache_lock);
+ 
+   p = node_list;
+   while (num_nodes-- > 0)
+-- 
+2.0.0.rc2
+