diff options
Diffstat (limited to 'debian/patches/0020-libdiskfs-lock-less-reference-counting-of-nodes.patch')
| -rw-r--r-- | debian/patches/0020-libdiskfs-lock-less-reference-counting-of-nodes.patch | 531 |
1 files changed, 531 insertions, 0 deletions
diff --git a/debian/patches/0020-libdiskfs-lock-less-reference-counting-of-nodes.patch b/debian/patches/0020-libdiskfs-lock-less-reference-counting-of-nodes.patch new file mode 100644 index 00000000..2142eb34 --- /dev/null +++ b/debian/patches/0020-libdiskfs-lock-less-reference-counting-of-nodes.patch @@ -0,0 +1,531 @@ +From 2bbb125dfe14d575401a924f4d5ac74c507cfc4b Mon Sep 17 00:00:00 2001 +From: Justus Winter <4winter@informatik.uni-hamburg.de> +Date: Wed, 14 May 2014 11:19:35 +0200 +Subject: [PATCH 20/27] libdiskfs: lock-less reference counting of nodes + +* libdiskfs/diskfs.h (struct node): Use refcounts_t for reference counting. +(diskfs_node_refcnt_lock): Remove. +(diskfs_node_norefs,diskfs_drop_node): Change comments accordingly. +* libdiskfs/init-init.c: Likewise. +* libdiskfs/node-drop.c: Likewise. +* libdiskfs/node-make.c: Likewise. +* libdiskfs/node-nput.c: Likewise. +* libdiskfs/node-nputl.c: Likewise. +* libdiskfs/node-nref.c: Likewise. +* libdiskfs/node-nrefl.c: Likewise. +* libdiskfs/node-nrele.c: Likewise. +* libdiskfs/node-nrelel.c: Likewise. +* ext2fs/inode.c: Likewise. +* fatfs/inode.c: Likewise. +* isofs/inode.c: Likewise. +* tmpfs/node.c: Likewise. +* doc/hurd.texi: Likewise. +--- + doc/hurd.texi | 11 ++-------- + ext2fs/inode.c | 9 +++------ + fatfs/inode.c | 21 ++++++------------- + isofs/inode.c | 9 +++------ + libdiskfs/diskfs.h | 12 ++++------- + libdiskfs/init-init.c | 2 -- + libdiskfs/node-drop.c | 9 +++------ + libdiskfs/node-make.c | 3 +-- + libdiskfs/node-nput.c | 54 +++++++++++++++++++------------------------------ + libdiskfs/node-nputl.c | 12 ++++------- + libdiskfs/node-nref.c | 10 ++++----- + libdiskfs/node-nrefl.c | 6 +++--- + libdiskfs/node-nrele.c | 48 +++++++++++++++++++++---------------------- + libdiskfs/node-nrelel.c | 9 +++------ + tmpfs/node.c | 9 +++------ + 15 files changed, 83 insertions(+), 141 deletions(-) + +diff --git a/doc/hurd.texi b/doc/hurd.texi +index 07ddfb4..6cafdb9 100644 +--- a/doc/hurd.texi ++++ b/doc/hurd.texi +@@ -3780,10 +3780,6 @@ new thread and (eventually) get rid of the old one; the old thread won't + do any more syncs, regardless. + @end deftypefun + +-@deftypevar spin_lock_t diskfs_node_refcnt_lock +-Pager reference count lock. +-@end deftypevar +- + @deftypevar int diskfs_readonly + Set to zero if the filesystem is currently writable. + @end deftypevar +@@ -3818,9 +3814,7 @@ Every file or directory is a diskfs @dfn{node}. The following functions + help your diskfs callbacks manage nodes and their references: + + @deftypefun void diskfs_drop_node (@w{struct node *@var{np}}) +-Node @var{np} now has no more references; clean all state. The +-@var{diskfs_node_refcnt_lock} must be held, and will be released upon +-return. @var{np} must be locked. ++Node @var{np} now has no more references; clean all state. + @end deftypefun + + @deftypefun void diskfs_node_update (@w{struct node *@var{np}}, @w{int @var{wait}}) +@@ -4236,14 +4230,13 @@ without real users. + @deftypefun void diskfs_try_dropping_softrefs (@w{struct node *@var{np}}) + Node @var{np} has some light references, but has just lost its last hard + references. Take steps so that if any light references can be freed, +-they are. Both @var{diskfs_node_refcnt_lock} and @var{np} are locked. ++they are. @var{np} is locked. + This function will be called after @code{diskfs_lost_hardrefs}. + @end deftypefun + + @deftypefun void diskfs_node_norefs (@w{struct node *@var{np}}) + Node @var{np} has no more references; free local state, including + @code{*@var{np}} if it shouldn't be retained. +-@var{diskfs_node_refcnt_lock} is held. + @end deftypefun + + @deftypefun error_t diskfs_set_hypermetadata (@w{int @var{wait}}, @w{int @var{clean}}) +diff --git a/ext2fs/inode.c b/ext2fs/inode.c +index aa070a2..7ec343f 100644 +--- a/ext2fs/inode.c ++++ b/ext2fs/inode.c +@@ -190,12 +190,9 @@ diskfs_try_dropping_softrefs (struct node *np) + { + /* 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); +- +- if (references > 0) ++ struct references result; ++ refcounts_references (&np->refcounts, &result); ++ if (result.hard > 0 || result.weak > 1) + { + /* A reference was reacquired through a hash table lookup. + It's fine, we didn't touch anything yet. */ +diff --git a/fatfs/inode.c b/fatfs/inode.c +index 8b3385b..d5750b4 100644 +--- a/fatfs/inode.c ++++ b/fatfs/inode.c +@@ -237,14 +237,8 @@ diskfs_node_norefs (struct node *np) + if (np->dn->translator) + free (np->dn->translator); + +- /* It is safe to unlock diskfs_node_refcnt_lock here for a while because +- all references to the node have been deleted. */ + if (np->dn->dirnode) +- { +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- diskfs_nrele (np->dn->dirnode); +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- } ++ diskfs_nrele (np->dn->dirnode); + + assert (!np->dn->pager); + +@@ -262,12 +256,9 @@ diskfs_try_dropping_softrefs (struct node *np) + { + /* 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); +- +- if (references > 0) ++ struct references result; ++ refcounts_references (&np->refcounts, &result); ++ if (result.hard > 0 || result.weak > 1) + { + /* A reference was reacquired through a hash table lookup. + It's fine, we didn't touch anything yet. */ +@@ -372,7 +363,7 @@ read_node (struct node *np, vm_address_t buf) + /* Files in fatfs depend on the directory that hold the file. */ + np->dn->dirnode = dp; + if (dp) +- dp->references++; ++ refcounts_ref (&dp->refcounts, NULL); + + pthread_rwlock_rdlock (&np->dn->dirent_lock); + +@@ -814,7 +805,7 @@ diskfs_alloc_node (struct node *dir, mode_t mode, struct node **node) + + /* FIXME: We know that readnode couldn't put this in. */ + np->dn->dirnode = dir; +- dir->references++; ++ refcounts_ref (&dir->refcounts, NULL); + + *node = np; + return 0; +diff --git a/isofs/inode.c b/isofs/inode.c +index 4f22086..b36a289 100644 +--- a/isofs/inode.c ++++ b/isofs/inode.c +@@ -536,12 +536,9 @@ diskfs_try_dropping_softrefs (struct node *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) ++ struct references result; ++ refcounts_references (&np->refcounts, &result); ++ if (result.hard > 0 || result.weak > 1) + { + /* A reference was reacquired through a hash table lookup. + It's fine, we didn't touch anything yet. */ +diff --git a/libdiskfs/diskfs.h b/libdiskfs/diskfs.h +index acd1910..e10e75e 100644 +--- a/libdiskfs/diskfs.h ++++ b/libdiskfs/diskfs.h +@@ -96,8 +96,7 @@ struct node + + pthread_mutex_t lock; + +- int references; /* hard references */ +- int light_references; /* light references */ ++ refcounts_t refcounts; + + mach_port_t sockaddr; /* address for S_IFSOCK shortcut */ + +@@ -201,8 +200,6 @@ extern volatile struct mapped_time_value *diskfs_mtime; + be done by format independent code. */ + extern int diskfs_synchronous; + +-extern pthread_spinlock_t diskfs_node_refcnt_lock; +- + extern int pager_port_type; + + /* Whether the filesystem is currently writable or not. */ +@@ -451,7 +448,7 @@ error_t diskfs_alloc_node (struct node *dp, mode_t mode, struct node **np); + void diskfs_free_node (struct node *np, mode_t mode); + + /* Node NP has no more references; free local state, including *NP +- if it isn't to be retained. diskfs_node_refcnt_lock is held. */ ++ if it isn't to be retained. */ + void diskfs_node_norefs (struct node *np); + + /* The user must define this function. Node NP has some light +@@ -614,9 +611,8 @@ void diskfs_spawn_first_thread (ports_demuxer_type demuxer); + diskfs_init_completed once it has a valid proc and auth port. */ + void diskfs_start_bootstrap (); + +-/* Node NP now has no more references; clean all state. The +- _diskfs_node_refcnt_lock must be held, and will be released +- upon return. NP must be locked. */ ++/* Node NP now has no more references; clean all state. NP must be ++ locked. */ + void diskfs_drop_node (struct node *np); + + /* Set on disk fields from NP->dn_stat; update ctime, atime, and mtime +diff --git a/libdiskfs/init-init.c b/libdiskfs/init-init.c +index 35be7ed..976b4e8 100644 +--- a/libdiskfs/init-init.c ++++ b/libdiskfs/init-init.c +@@ -37,8 +37,6 @@ int _diskfs_noatime; + + struct hurd_port _diskfs_exec_portcell; + +-pthread_spinlock_t diskfs_node_refcnt_lock = PTHREAD_SPINLOCK_INITIALIZER; +- + pthread_spinlock_t _diskfs_control_lock = PTHREAD_SPINLOCK_INITIALIZER; + int _diskfs_ncontrol_ports; + +diff --git a/libdiskfs/node-drop.c b/libdiskfs/node-drop.c +index 83eb590..fab3cfa 100644 +--- a/libdiskfs/node-drop.c ++++ b/libdiskfs/node-drop.c +@@ -31,9 +31,8 @@ free_modreqs (struct modreq *mr) + } + + +-/* Node NP now has no more references; clean all state. The +- diskfs_node_refcnt_lock must be held, and will be released +- upon return. NP must be locked. */ ++/* Node NP now has no more references; clean all state. NP must be ++ locked. */ + void + diskfs_drop_node (struct node *np) + { +@@ -60,8 +59,7 @@ diskfs_drop_node (struct node *np) + and an nput. The next time through, this routine + will notice that the size is zero, and not have to + do anything. */ +- np->references++; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ refcounts_ref (&np->refcounts, NULL); + diskfs_truncate (np, 0); + + /* Force allocsize to zero; if truncate consistently fails this +@@ -94,5 +92,4 @@ diskfs_drop_node (struct node *np) + assert (!np->sockaddr); + + diskfs_node_norefs (np); +- pthread_spin_unlock (&diskfs_node_refcnt_lock); + } +diff --git a/libdiskfs/node-make.c b/libdiskfs/node-make.c +index ff0cc0d..c7ca3b0 100644 +--- a/libdiskfs/node-make.c ++++ b/libdiskfs/node-make.c +@@ -29,8 +29,7 @@ init_node (struct node *np, struct disknode *dn) + np->dn_stat_dirty = 0; + + pthread_mutex_init (&np->lock, NULL); +- np->references = 1; +- np->light_references = 0; ++ refcounts_init (&np->refcounts, 1, 0); + np->owner = 0; + np->sockaddr = MACH_PORT_NULL; + +diff --git a/libdiskfs/node-nput.c b/libdiskfs/node-nput.c +index 5043ad1..2935ae2 100644 +--- a/libdiskfs/node-nput.c ++++ b/libdiskfs/node-nput.c +@@ -26,56 +26,44 @@ + void + diskfs_nput (struct node *np) + { +- int tried_drop_softrefs = 0; ++ struct references result; + +- loop: +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- assert (np->references); +- np->references--; +- if (np->references + np->light_references == 0) +- diskfs_drop_node (np); +- else if (np->references == 0 && !tried_drop_softrefs) +- { +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ /* While we call the diskfs_try_dropping_softrefs, we need to hold ++ one reference. We use a weak reference for this purpose, which ++ we acquire by demoting our hard reference to a weak one. */ ++ refcounts_demote (&np->refcounts, &result); + ++ if (result.hard == 0) ++ { + /* This is our cue that something akin to "last process closes file" + in the POSIX.1 sense happened, so make sure any pending node time + updates now happen in a timely fashion. */ + diskfs_set_node_times (np); +- + diskfs_lost_hardrefs (np); + if (!np->dn_stat.st_nlink) + { +- /* There are no links. If there are soft references that +- can be dropped, we can't let them postpone deallocation. +- So attempt to drop them. But that's a user-supplied +- routine, which might result in further recursive calls to +- the ref-counting system. So we have to reacquire our +- reference around the call to forestall disaster. */ +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- np->references++; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- + if (np->sockaddr != MACH_PORT_NULL) + { + mach_port_deallocate (mach_task_self (), np->sockaddr); + np->sockaddr = MACH_PORT_NULL; + } + ++ /* There are no links. If there are soft references that ++ can be dropped, we can't let them postpone deallocation. ++ So attempt to drop them. But that's a user-supplied ++ routine, which might result in further recursive calls to ++ the ref-counting system. This is not a problem, as we ++ hold a weak reference ourselves. */ + diskfs_try_dropping_softrefs (np); +- +- /* But there's no value in looping forever in this +- routine; only try to drop soft refs once. */ +- tried_drop_softrefs = 1; +- +- /* Now we can drop the reference back... */ +- goto loop; + } + pthread_mutex_unlock (&np->lock); + } +- else +- { +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- pthread_mutex_unlock (&np->lock); +- } ++ ++ /* Finally get rid of our reference. */ ++ refcounts_deref_weak (&np->refcounts, &result); ++ ++ if (result.hard == 0 && result.weak == 0) ++ diskfs_drop_node (np); ++ ++ pthread_mutex_unlock (&np->lock); + } +diff --git a/libdiskfs/node-nputl.c b/libdiskfs/node-nputl.c +index 1959665..8dac16e 100644 +--- a/libdiskfs/node-nputl.c ++++ b/libdiskfs/node-nputl.c +@@ -25,14 +25,10 @@ + void + diskfs_nput_light (struct node *np) + { +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- assert (np->light_references); +- np->light_references--; +- if (np->references + np->light_references == 0) ++ struct references result; ++ refcounts_deref_weak (&np->refcounts, &result); ++ if (result.hard == 0 && result.weak == 0) + diskfs_drop_node (np); + else +- { +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- pthread_mutex_unlock (&np->lock); +- } ++ pthread_mutex_unlock (&np->lock); + } +diff --git a/libdiskfs/node-nref.c b/libdiskfs/node-nref.c +index 13cea05..89ffa4f 100644 +--- a/libdiskfs/node-nref.c ++++ b/libdiskfs/node-nref.c +@@ -26,12 +26,10 @@ + void + diskfs_nref (struct node *np) + { +- int new_hardref; +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- np->references++; +- new_hardref = (np->references == 1); +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- if (new_hardref) ++ struct references result; ++ refcounts_ref (&np->refcounts, &result); ++ assert (result.hard > 1 || result.weak > 0); ++ if (result.hard == 1) + { + pthread_mutex_lock (&np->lock); + diskfs_new_hardrefs (np); +diff --git a/libdiskfs/node-nrefl.c b/libdiskfs/node-nrefl.c +index 9692247..b7af409 100644 +--- a/libdiskfs/node-nrefl.c ++++ b/libdiskfs/node-nrefl.c +@@ -24,7 +24,7 @@ + void + diskfs_nref_light (struct node *np) + { +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- np->light_references++; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ struct references result; ++ refcounts_ref_weak (&np->refcounts, &result); ++ assert (result.hard > 0 || result.weak > 1); + } +diff --git a/libdiskfs/node-nrele.c b/libdiskfs/node-nrele.c +index cc68089..d962846 100644 +--- a/libdiskfs/node-nrele.c ++++ b/libdiskfs/node-nrele.c +@@ -28,38 +28,36 @@ + void + diskfs_nrele (struct node *np) + { +- int tried_drop_softrefs = 0; ++ struct references result; + +- loop: +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- assert (np->references); +- np->references--; +- if (np->references + np->light_references == 0) +- { +- pthread_mutex_lock (&np->lock); +- diskfs_drop_node (np); +- } +- else if (np->references == 0) ++ /* While we call the diskfs_try_dropping_softrefs, we need to hold ++ one reference. We use a weak reference for this purpose, which ++ we acquire by demoting our hard reference to a weak one. */ ++ refcounts_demote (&np->refcounts, &result); ++ ++ if (result.hard == 0) + { + pthread_mutex_lock (&np->lock); +- pthread_spin_unlock (&diskfs_node_refcnt_lock); + diskfs_lost_hardrefs (np); +- if (!np->dn_stat.st_nlink && !tried_drop_softrefs) ++ if (!np->dn_stat.st_nlink) + { +- /* Same issue here as in nput; see that for explanation */ +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- np->references++; +- pthread_spin_unlock (&diskfs_node_refcnt_lock); +- ++ /* There are no links. If there are soft references that ++ can be dropped, we can't let them postpone deallocation. ++ So attempt to drop them. But that's a user-supplied ++ routine, which might result in further recursive calls to ++ the ref-counting system. This is not a problem, as we ++ hold a weak reference ourselves. */ + diskfs_try_dropping_softrefs (np); +- tried_drop_softrefs = 1; +- +- /* Now we can drop the reference back... */ +- pthread_mutex_unlock (&np->lock); +- goto loop; + } + pthread_mutex_unlock (&np->lock); + } +- else +- pthread_spin_unlock (&diskfs_node_refcnt_lock); ++ ++ /* Finally get rid of our reference. */ ++ refcounts_deref_weak (&np->refcounts, &result); ++ ++ if (result.hard == 0 && result.weak == 0) ++ { ++ pthread_mutex_lock (&np->lock); ++ diskfs_drop_node (np); ++ } + } +diff --git a/libdiskfs/node-nrelel.c b/libdiskfs/node-nrelel.c +index ee53b22..dc4f920 100644 +--- a/libdiskfs/node-nrelel.c ++++ b/libdiskfs/node-nrelel.c +@@ -26,14 +26,11 @@ + void + diskfs_nrele_light (struct node *np) + { +- pthread_spin_lock (&diskfs_node_refcnt_lock); +- assert (np->light_references); +- np->light_references--; +- if (np->references + np->light_references == 0) ++ struct references result; ++ refcounts_deref_weak (&np->refcounts, &result); ++ if (result.hard == 0 && result.weak == 0) + { + pthread_mutex_lock (&np->lock); + diskfs_drop_node (np); + } +- else +- pthread_spin_unlock (&diskfs_node_refcnt_lock); + } +diff --git a/tmpfs/node.c b/tmpfs/node.c +index 74971ec..275bb3c 100644 +--- a/tmpfs/node.c ++++ b/tmpfs/node.c +@@ -285,12 +285,9 @@ diskfs_try_dropping_softrefs (struct node *np) + { + /* 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) ++ struct references result; ++ refcounts_references (&np->refcounts, &result); ++ if (result.hard > 0 || result.weak > 1) + { + /* A reference was reacquired through a hash table lookup. + It's fine, we didn't touch anything yet. */ +-- +2.0.0.rc2 + |