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Diffstat (limited to 'ext2fs/inode.c')
-rw-r--r--ext2fs/inode.c128
1 files changed, 92 insertions, 36 deletions
diff --git a/ext2fs/inode.c b/ext2fs/inode.c
index 6b8b7499..7c8d5a8c 100644
--- a/ext2fs/inode.c
+++ b/ext2fs/inode.c
@@ -46,8 +46,19 @@
#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;
+/* nodecache_lock must be acquired before diskfs_node_refcnt_lock. */
+static pthread_rwlock_t nodecache_lock = PTHREAD_RWLOCK_INITIALIZER;
static error_t read_node (struct node *np);
@@ -62,33 +73,37 @@ inode_init ()
nodehash[n] = 0;
}
+/* Lookup node with inode number INUM. Returns NULL if the node is
+ not found in the node cache. */
+static struct node *
+lookup (ino_t inum)
+{
+ struct node *np;
+ for (np = nodehash[INOHASH(inum)]; np; np = np->dn->hnext)
+ if (np->cache_id == inum)
+ return np;
+ return NULL;
+}
+
/* Fetch inode INUM, set *NPP to the node structure;
gain one user reference and lock the node. */
error_t
diskfs_cached_lookup (ino_t inum, struct node **npp)
{
error_t err;
- struct node *np;
+ struct node *np, *tmp;
struct disknode *dn;
- pthread_spin_lock (&diskfs_node_refcnt_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);
- pthread_mutex_lock (&np->lock);
- *npp = np;
- return 0;
- }
+ pthread_rwlock_rdlock (&nodecache_lock);
+ np = lookup (inum);
+ if (np)
+ goto gotit;
+ 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 +117,24 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
pthread_mutex_lock (&np->lock);
/* Put NP in NODEHASH. */
+ pthread_rwlock_wrlock (&nodecache_lock);
+ tmp = lookup (inum);
+ if (tmp)
+ {
+ /* We lost a race. */
+ diskfs_nput (np);
+ np = tmp;
+ goto gotit;
+ }
+
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);
@@ -131,6 +156,13 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
*npp = np;
return 0;
}
+
+ gotit:
+ diskfs_nref (np);
+ pthread_rwlock_unlock (&nodecache_lock);
+ pthread_mutex_lock (&np->lock);
+ *npp = np;
+ return 0;
}
/* Lookup node INUM (which must have a reference already) and return it
@@ -140,17 +172,12 @@ ifind (ino_t inum)
{
struct node *np;
- pthread_spin_lock (&diskfs_node_refcnt_lock);
- for (np = nodehash[INOHASH(inum)]; np; np = np->dn->hnext)
- {
- if (np->cache_id != inum)
- continue;
+ pthread_rwlock_rdlock (&nodecache_lock);
+ np = lookup (inum);
+ pthread_rwlock_unlock (&nodecache_lock);
- assert (np->references);
- pthread_spin_unlock (&diskfs_node_refcnt_lock);
- return np;
- }
- assert (0);
+ assert (np);
+ return np;
}
/* The last reference to a node has gone away; drop
@@ -158,11 +185,6 @@ 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 +202,36 @@ diskfs_node_norefs (struct node *np)
void
diskfs_try_dropping_softrefs (struct node *np)
{
+ pthread_rwlock_wrlock (&nodecache_lock);
+ if (np->dn->hprevp != 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;
+ np->dn->hprevp = NULL;
+ nodehash_nr_items -= 1;
+ diskfs_nrele_light (np);
+ }
+ pthread_rwlock_unlock (&nodecache_lock);
+
drop_pager_softrefs (np);
}
@@ -556,12 +608,12 @@ 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 +622,7 @@ 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 +632,14 @@ diskfs_node_iterate (error_t (*fun)(struct node *))
for (node = nodehash[n]; node; node = node->dn->hnext)
{
*p++ = node;
+
+ /* 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)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 07:53:14 +0000