summaryrefslogtreecommitdiff
path: root/tmpfs/node.c
diff options
context:
space:
mode:
Diffstat (limited to 'tmpfs/node.c')
-rw-r--r--tmpfs/node.c107
1 files changed, 78 insertions, 29 deletions
diff --git a/tmpfs/node.c b/tmpfs/node.c
index 02d7a603..428b6d92 100644
--- a/tmpfs/node.c
+++ b/tmpfs/node.c
@@ -29,8 +29,19 @@
unsigned int num_files;
static unsigned int gen;
+/* all_nodes is a list of all nodes.
+
+ Access to all_nodes and all_nodes_nr_items is protected by
+ all_nodes_lock.
+
+ Every node in all_nodes 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. */
struct node *all_nodes;
static size_t all_nodes_nr_items;
+/* all_nodes_lock must be acquired before diskfs_node_refcnt_lock. */
+pthread_rwlock_t all_nodes_lock = PTHREAD_RWLOCK_INITIALIZER;
error_t
diskfs_alloc_node (struct node *dp, mode_t mode, struct node **npp)
@@ -40,18 +51,17 @@ diskfs_alloc_node (struct node *dp, mode_t mode, struct node **npp)
dn = calloc (1, sizeof *dn);
if (dn == 0)
return ENOSPC;
- pthread_spin_lock (&diskfs_node_refcnt_lock);
- if (round_page (tmpfs_space_used + sizeof *dn) / vm_page_size
+
+ if (round_page (get_used () + sizeof *dn) / vm_page_size
> tmpfs_page_limit)
{
- pthread_spin_unlock (&diskfs_node_refcnt_lock);
+ pthread_rwlock_unlock (&all_nodes_lock);
free (dn);
return ENOSPC;
}
dn->gen = gen++;
- ++num_files;
- tmpfs_space_used += sizeof *dn;
- pthread_spin_unlock (&diskfs_node_refcnt_lock);
+ __atomic_add_fetch (&num_files, 1, __ATOMIC_RELAXED);
+ adjust_used (sizeof *dn);
dn->type = IFTODT (mode & S_IFMT);
return diskfs_cached_lookup ((ino_t) (uintptr_t) dn, npp);
@@ -75,15 +85,19 @@ diskfs_free_node (struct node *np, mode_t mode)
free (np->dn->u.lnk);
break;
}
+
+ pthread_rwlock_wrlock (&all_nodes_lock);
*np->dn->hprevp = np->dn->hnext;
if (np->dn->hnext != 0)
np->dn->hnext->dn->hprevp = np->dn->hprevp;
all_nodes_nr_items -= 1;
+ pthread_rwlock_unlock (&all_nodes_lock);
+
free (np->dn);
np->dn = 0;
- --num_files;
- tmpfs_space_used -= sizeof *np->dn;
+ __atomic_sub_fetch (&num_files, 1, __ATOMIC_RELAXED);
+ adjust_used (-sizeof *np->dn);
}
void
@@ -117,14 +131,6 @@ diskfs_node_norefs (struct node *np)
np->dn->u.chr = np->dn_stat.st_rdev;
break;
}
-
- /* Remove this node from the cache list rooted at `all_nodes'. */
- *np->dn->hprevp = np->dn->hnext;
- if (np->dn->hnext != 0)
- np->dn->hnext->dn->hprevp = np->dn->hprevp;
- all_nodes_nr_items -= 1;
- np->dn->hnext = 0;
- np->dn->hprevp = 0;
}
free (np);
@@ -167,30 +173,34 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
assert (npp);
+ pthread_rwlock_rdlock (&all_nodes_lock);
if (dn->hprevp != 0) /* There is already a node. */
- {
- np = *dn->hprevp;
- assert (np->dn == dn);
- assert (*dn->hprevp == np);
-
- diskfs_nref (np);
- }
+ goto gotit;
else
/* Create the new node. */
{
struct stat *st;
+ pthread_rwlock_unlock (&all_nodes_lock);
np = diskfs_make_node (dn);
np->cache_id = (ino_t) (uintptr_t) dn;
- pthread_spin_lock (&diskfs_node_refcnt_lock);
+ pthread_rwlock_wrlock (&all_nodes_lock);
+ if (dn->hprevp != NULL)
+ {
+ /* We lost a race. */
+ diskfs_nrele (np);
+ goto gotit;
+ }
+
dn->hnext = all_nodes;
if (dn->hnext)
dn->hnext->dn->hprevp = &dn->hnext;
dn->hprevp = &all_nodes;
all_nodes = np;
all_nodes_nr_items += 1;
- pthread_spin_unlock (&diskfs_node_refcnt_lock);
+ diskfs_nref_light (np);
+ pthread_rwlock_unlock (&all_nodes_lock);
st = &np->dn_stat;
memset (st, 0, sizeof *st);
@@ -220,6 +230,16 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
pthread_mutex_lock (&np->lock);
*npp = np;
return 0;
+
+ gotit:
+ np = *dn->hprevp;
+ assert (np->dn == dn);
+ assert (*dn->hprevp == np);
+ diskfs_nref (np);
+ pthread_rwlock_unlock (&all_nodes_lock);
+ pthread_mutex_lock (&np->lock);
+ *npp = np;
+ return 0;
}
error_t
@@ -229,12 +249,12 @@ 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 (&all_nodes_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
+ all_nodes_lock, but we can't hold this while locking the
individual node locks). */
num_nodes = all_nodes_nr_items;
@@ -243,10 +263,14 @@ diskfs_node_iterate (error_t (*fun) (struct node *))
for (node = all_nodes; node != 0; 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 (&all_nodes_lock);
p = node_list;
while (num_nodes-- > 0)
@@ -272,6 +296,31 @@ diskfs_node_iterate (error_t (*fun) (struct node *))
void
diskfs_try_dropping_softrefs (struct node *np)
{
+ pthread_rwlock_wrlock (&all_nodes_lock);
+ if (np->cache_id != 0)
+ {
+ /* Check if someone reacquired a reference. */
+ 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. It's fine, we didn't touch
+ anything yet. */
+ pthread_rwlock_unlock (&all_nodes_lock);
+ return;
+ }
+
+ /* Just let go of the weak reference. The node will be removed
+ from all_nodes in diskfs_free_node. */
+ np->cache_id = 0;
+ diskfs_nrele_light (np);
+ }
+ pthread_rwlock_unlock (&all_nodes_lock);
}
/* The user must define this funcction. Node NP has some light
@@ -447,7 +496,7 @@ diskfs_grow (struct node *np, off_t size, struct protid *cred)
off_t set_size = size;
size = round_page (size);
- if (round_page (tmpfs_space_used + size - np->allocsize)
+ if (round_page (get_used () + size - np->allocsize)
/ vm_page_size > tmpfs_page_limit)
return ENOSPC;
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-27 13:37:54 +0000