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authorJustus Winter <4winter@informatik.uni-hamburg.de>2014-05-16 13:25:36 +0200
committerJustus Winter <4winter@informatik.uni-hamburg.de>2014-05-16 13:25:36 +0200
commit44544936e40a55c6cae9983f1079dd67749347a3 (patch)
treee8d14a67e361ccc1dcd27a62df6b13155255aa66 /debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch
parentb39a4dca84393407806cb8a8b0630db1993bc38e (diff)
add patch series
Diffstat (limited to 'debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch')
-rw-r--r--debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch222
1 files changed, 222 insertions, 0 deletions
diff --git a/debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch b/debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch
new file mode 100644
index 00000000..1b5fe5fe
--- /dev/null
+++ b/debian/patches/0018-isofs-use-a-seperate-lock-to-protect-node_cache.patch
@@ -0,0 +1,222 @@
+From 759d9be9624ac9426d1b66ea96999152f5dd60ea Mon Sep 17 00:00:00 2001
+From: Justus Winter <4winter@informatik.uni-hamburg.de>
+Date: Tue, 13 May 2014 15:16:31 +0200
+Subject: [PATCH 18/20] isofs: use a seperate lock to protect node_cache
+
+Previously, isofs used diskfs_node_refcnt_lock to serialize access to
+the node_cache.
+
+Use a separate lock to protect node_cache. Adjust the reference
+counting accordingly. Every node in the node_cache 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 node_cache.
+
+* isofs/inode.c (node_cache_lock): New lock.
+(inode_cache_find): Use a separate lock to protect node_cache.
+Adjust the reference counting accordingly.
+(diskfs_cached_lookup): Likewise.
+(load_inode): Likewise.
+(cache_inode): Update comment accordingly.
+(diskfs_node_iterate): Likewise.
+(diskfs_node_norefs): Move the code removing the node from node_cache...
+(diskfs_try_dropping_softrefs): ... here, where we check whether
+someone reacquired a reference, and if so hold on to our light
+reference.
+---
+ isofs/inode.c | 72 +++++++++++++++++++++++++++++++++++++++++++----------------
+ 1 file changed, 53 insertions(+), 19 deletions(-)
+
+diff --git a/isofs/inode.c b/isofs/inode.c
+index cdc05ae..4f22086 100644
+--- a/isofs/inode.c
++++ b/isofs/inode.c
+@@ -48,9 +48,19 @@ struct node_cache
+ struct node *np; /* if live */
+ };
+
++/* The node_cache is a cache of nodes.
++
++ Access to node_cache, node_cache_size, and node_cache_alloced is
++ protected by node_cache_lock.
++
++ Every node in the node_cache 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 node_cache. */
+ static int node_cache_size = 0;
+ static int node_cache_alloced = 0;
+ struct node_cache *node_cache = 0;
++static pthread_mutex_t node_cache_lock = PTHREAD_MUTEX_INITIALIZER;
+
+ /* Forward */
+ static error_t read_disknode (struct node *,
+@@ -58,7 +68,7 @@ static error_t read_disknode (struct node *,
+
+
+ /* See if node with identifier ID is in the cache. If so, return it,
+- with one additional reference. diskfs_node_refcnt_lock must be held
++ with one additional reference. node_cache_lock must be held
+ on entry to the call, and will be released iff the node was found
+ in the cache. */
+ void
+@@ -71,8 +81,8 @@ inode_cache_find (off_t id, struct node **npp)
+ && node_cache[i].np)
+ {
+ *npp = node_cache[i].np;
+- (*npp)->references++;
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ diskfs_nref (*npp);
++ pthread_mutex_unlock (&node_cache_lock);
+ pthread_mutex_lock (&(*npp)->lock);
+ return;
+ }
+@@ -92,7 +102,7 @@ use_file_start_id (struct dirrect *record, struct rrip_lookup *rr)
+ }
+
+ /* Enter NP into the cache. The directory entry we used is DR, the
+- cached Rock-Ridge info RR. diskfs_node_refcnt_lock must be held. */
++ cached Rock-Ridge info RR. node_cache_lock must be held. */
+ void
+ cache_inode (struct node *np, struct dirrect *record,
+ struct rrip_lookup *rr)
+@@ -155,7 +165,7 @@ diskfs_cached_lookup (ino_t id, struct node **npp)
+ to avoid presenting zero cache ID's. */
+ id--;
+
+- pthread_spin_lock (&diskfs_node_refcnt_lock);
++ pthread_mutex_lock (&node_cache_lock);
+ assert (id < node_cache_size);
+
+ np = node_cache[id].np;
+@@ -174,7 +184,7 @@ diskfs_cached_lookup (ino_t id, struct node **npp)
+ dn = malloc (sizeof (struct disknode));
+ if (!dn)
+ {
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+ release_rrip (&rr);
+ return ENOMEM;
+ }
+@@ -185,16 +195,17 @@ diskfs_cached_lookup (ino_t id, struct node **npp)
+ if (!np)
+ {
+ free (dn);
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+ release_rrip (&rr);
+ return ENOMEM;
+ }
+ np->cache_id = id + 1; /* see above for rationale for increment */
+ pthread_mutex_lock (&np->lock);
+ c->np = np;
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ diskfs_nref_light (np);
++ pthread_mutex_unlock (&node_cache_lock);
+
+- err = read_disknode (np, node_cache[id].dr, &rr);
++ err = read_disknode (np, dn->dr, &rr);
+ if (!err)
+ *npp = np;
+
+@@ -204,8 +215,8 @@ diskfs_cached_lookup (ino_t id, struct node **npp)
+ }
+
+
+- np->references++;
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ diskfs_nref (np);
++ pthread_mutex_unlock (&node_cache_lock);
+ pthread_mutex_lock (&np->lock);
+ *npp = np;
+ return 0;
+@@ -315,7 +326,7 @@ load_inode (struct node **npp, struct dirrect *record,
+ if (rr->valid & VALID_CL)
+ record = rr->realdirent;
+
+- pthread_spin_lock (&diskfs_node_refcnt_lock);
++ pthread_mutex_lock (&node_cache_lock);
+
+ /* First check the cache */
+ if (use_file_start_id (record, rr))
+@@ -325,7 +336,7 @@ load_inode (struct node **npp, struct dirrect *record,
+
+ if (*npp)
+ {
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+ return 0;
+ }
+
+@@ -333,7 +344,7 @@ load_inode (struct node **npp, struct dirrect *record,
+ dn = malloc (sizeof (struct disknode));
+ if (!dn)
+ {
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+ return ENOMEM;
+ }
+ dn->fileinfo = 0;
+@@ -344,14 +355,14 @@ load_inode (struct node **npp, struct dirrect *record,
+ if (!np)
+ {
+ free (dn);
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+ return ENOMEM;
+ }
+
+ pthread_mutex_lock (&np->lock);
+
+ cache_inode (np, record, rr);
+- pthread_spin_unlock (&diskfs_node_refcnt_lock);
++ pthread_mutex_unlock (&node_cache_lock);
+
+ err = read_disknode (np, record, rr);
+ *npp = np;
+@@ -505,9 +516,6 @@ error_t (*diskfs_read_symlink_hook) (struct node *, char *)
+ void
+ diskfs_node_norefs (struct node *np)
+ {
+- assert (node_cache[np->cache_id - 1].np == np);
+- node_cache[np->cache_id - 1].np = 0;
+-
+ if (np->dn->translator)
+ free (np->dn->translator);
+
+@@ -521,6 +529,32 @@ diskfs_node_norefs (struct node *np)
+ void
+ diskfs_try_dropping_softrefs (struct node *np)
+ {
++ pthread_mutex_lock (&node_cache_lock);
++ if (np->cache_id != 0)
++ {
++ assert (node_cache[np->cache_id - 1].np == np);
++
++ /* Check if someone reacquired a reference through the
++ node_cache. */
++ unsigned int references;
++ pthread_spin_lock (&diskfs_node_refcnt_lock);
++ references = np->references;
++ pthread_spin_unlock (&diskfs_node_refcnt_lock);
++
++ if (references > 0)
++ {
++ /* A reference was reacquired through a hash table lookup.
++ It's fine, we didn't touch anything yet. */
++ pthread_mutex_unlock (&node_cache_lock);
++ return;
++ }
++
++ node_cache[np->cache_id - 1].np = 0;
++ np->cache_id = 0;
++ diskfs_nrele_light (np);
++ }
++ pthread_mutex_unlock (&node_cache_lock);
++
+ drop_pager_softrefs (np);
+ }
+
+--
+2.0.0.rc0
+