diff options
Diffstat (limited to 'debian/patches/0018-tmpfs-use-a-seperate-lock-to-protect-all_nodes.patch')
| -rw-r--r-- | debian/patches/0018-tmpfs-use-a-seperate-lock-to-protect-all_nodes.patch | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/debian/patches/0018-tmpfs-use-a-seperate-lock-to-protect-all_nodes.patch b/debian/patches/0018-tmpfs-use-a-seperate-lock-to-protect-all_nodes.patch new file mode 100644 index 00000000..75061085 --- /dev/null +++ b/debian/patches/0018-tmpfs-use-a-seperate-lock-to-protect-all_nodes.patch @@ -0,0 +1,272 @@ +From 169ef4426b3237510025287ff5dcfb83cc143982 Mon Sep 17 00:00:00 2001 +From: Justus Winter <4winter@informatik.uni-hamburg.de> +Date: Tue, 13 May 2014 15:35:42 +0200 +Subject: [PATCH 18/20] tmpfs: use a seperate lock to protect all_nodes + +Previously, tmpfs used diskfs_node_refcnt_lock to serialize access to +the all_nodes and some other related global state related to memory +consumption. + +Use a separate lock to protect all_nodes, and to the state related to +memory consumption as this is updated during insertion and removal +operations. Adjust the reference counting accordingly. Every node in +the 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 through the all_nodes. + +* tmpfs/node.c (all_nodes_lock): New lock. +(diskfs_alloc_node): Use a separate lock to protect all_nodes. +Adjust the reference counting accordingly. +(diskfs_free_node): Likewise. +(diskfs_cached_lookup):Likewise. +(diskfs_node_iterate): Likewise. +(diskfs_node_norefs): Move the code removing the node from all_nodes... +(diskfs_try_dropping_softrefs): ... here, where we check whether +someone reacquired a reference, and if so hold on to our light +reference. +* tmpfs/tmpfs.c (diskfs_set_statfs): Use all_nodes_lock. +* tmpfs/tmpfs.h (all_nodes_lock): New declaration. +(adjust_used): Use all_nodes_lock. +--- + tmpfs/node.c | 78 +++++++++++++++++++++++++++++++++++++++++++---------------- + tmpfs/tmpfs.c | 4 +-- + tmpfs/tmpfs.h | 6 +++-- + 3 files changed, 63 insertions(+), 25 deletions(-) + +diff --git a/tmpfs/node.c b/tmpfs/node.c +index acc029a..689777f 100644 +--- a/tmpfs/node.c ++++ b/tmpfs/node.c +@@ -29,8 +29,18 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ + unsigned int num_files; + static unsigned int gen; + ++/* all_nodes is a cache of nodes. ++ ++ Access to all_nodes and all_nodes_nr_items is protected by ++ all_nodes_lock. ++ ++ Every node in the 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 ++ through the all_nodes. */ + struct node *all_nodes; + static size_t all_nodes_nr_items; ++pthread_mutex_t all_nodes_lock = PTHREAD_MUTEX_INITIALIZER; + + error_t + diskfs_alloc_node (struct node *dp, mode_t mode, struct node **npp) +@@ -40,18 +50,18 @@ 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); ++ pthread_mutex_lock (&all_nodes_lock); + if (round_page (tmpfs_space_used + sizeof *dn) / vm_page_size + > tmpfs_page_limit) + { +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ pthread_mutex_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); ++ pthread_mutex_unlock (&all_nodes_lock); + + dn->type = IFTODT (mode & S_IFMT); + return diskfs_cached_lookup ((ino_t) (uintptr_t) dn, npp); +@@ -75,15 +85,18 @@ diskfs_free_node (struct node *np, mode_t mode) + free (np->dn->u.lnk); + break; + } ++ ++ pthread_mutex_lock (&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; +- free (np->dn); +- np->dn = 0; +- + --num_files; + tmpfs_space_used -= sizeof *np->dn; ++ pthread_mutex_unlock (&all_nodes_lock); ++ ++ free (np->dn); ++ np->dn = 0; + } + + void +@@ -117,14 +130,6 @@ 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); +@@ -167,11 +172,14 @@ diskfs_cached_lookup (ino_t inum, struct node **npp) + + assert (npp); + ++ pthread_mutex_lock (&all_nodes_lock); ++ + if (dn->hprevp != 0) /* There is already a node. */ + { + np = *dn->hprevp; + assert (np->dn == dn); + assert (*dn->hprevp == np); ++ pthread_mutex_unlock (&all_nodes_lock); + + diskfs_nref (np); + } +@@ -183,14 +191,14 @@ diskfs_cached_lookup (ino_t inum, struct node **npp) + np = diskfs_make_node (dn); + np->cache_id = (ino_t) (uintptr_t) dn; + +- pthread_spin_lock (&diskfs_node_refcnt_lock); + 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_mutex_unlock (&all_nodes_lock); + + st = &np->dn_stat; + memset (st, 0, sizeof *st); +@@ -229,12 +237,12 @@ 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_mutex_lock (&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 +251,10 @@ diskfs_node_iterate (error_t (*fun) (struct node *)) + for (node = all_nodes; node != 0; node = node->dn->hnext) + { + *p++ = node; +- node->references++; ++ diskfs_nref_light (node); + } + +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ pthread_mutex_unlock (&all_nodes_lock); + + p = node_list; + while (num_nodes-- > 0) +@@ -258,7 +266,7 @@ diskfs_node_iterate (error_t (*fun) (struct node *)) + err = (*fun) (node); + pthread_mutex_unlock (&node->lock); + } +- diskfs_nrele (node); ++ diskfs_nrele_light (node); + } + + return err; +@@ -272,6 +280,34 @@ diskfs_node_iterate (error_t (*fun) (struct node *)) + void + diskfs_try_dropping_softrefs (struct node *np) + { ++ pthread_mutex_lock (&all_nodes_lock); ++ if (np->dn->hnext != NULL) ++ { ++ /* Check if someone reacquired a reference through the ++ all_nodes. */ ++ 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 (&all_nodes_lock); ++ return; ++ } ++ ++ /* 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 = NULL; ++ np->dn->hprevp = NULL; ++ diskfs_nrele_light (np); ++ } ++ pthread_mutex_unlock (&all_nodes_lock); + } + + /* The user must define this funcction. Node NP has some light +diff --git a/tmpfs/tmpfs.c b/tmpfs/tmpfs.c +index a45d343..024b818 100644 +--- a/tmpfs/tmpfs.c ++++ b/tmpfs/tmpfs.c +@@ -67,10 +67,10 @@ diskfs_set_statfs (struct statfs *st) + st->f_bsize = vm_page_size; + st->f_blocks = tmpfs_page_limit; + +- pthread_spin_lock (&diskfs_node_refcnt_lock); ++ pthread_mutex_lock (&all_nodes_lock); + st->f_files = num_files; + pages = round_page (tmpfs_space_used) / vm_page_size; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ pthread_mutex_unlock (&all_nodes_lock); + + st->f_bfree = pages < tmpfs_page_limit ? tmpfs_page_limit - pages : 0; + st->f_bavail = st->f_bfree; +diff --git a/tmpfs/tmpfs.h b/tmpfs/tmpfs.h +index b3c636d..187249e 100644 +--- a/tmpfs/tmpfs.h ++++ b/tmpfs/tmpfs.h +@@ -24,6 +24,7 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ + #include <sys/types.h> + #include <dirent.h> + #include <stdint.h> ++#include <pthread.h> + + struct disknode + { +@@ -71,15 +72,16 @@ struct tmpfs_dirent + + extern unsigned int num_files; + extern off_t tmpfs_page_limit, tmpfs_space_used; ++extern pthread_mutex_t all_nodes_lock; + + extern mach_port_t default_pager; + + static inline void + adjust_used (off_t change) + { +- pthread_spin_lock (&diskfs_node_refcnt_lock); ++ pthread_mutex_lock (&all_nodes_lock); + tmpfs_space_used += change; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ pthread_mutex_unlock (&all_nodes_lock); + } + + #endif +-- +2.0.0.rc2 + |