diff options
| -rw-r--r-- | fs/btrfs/Makefile | 2 | ||||
| -rw-r--r-- | fs/btrfs/ulist.c | 220 | ||||
| -rw-r--r-- | fs/btrfs/ulist.h | 68 |
3 files changed, 289 insertions, 1 deletions
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile index c0ddfd29c5e..70798407b9a 100644 --- a/fs/btrfs/Makefile +++ b/fs/btrfs/Makefile @@ -8,6 +8,6 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \ extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \ export.o tree-log.o free-space-cache.o zlib.o lzo.o \ compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \ - reada.o backref.o + reada.o backref.o ulist.o btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c new file mode 100644 index 00000000000..12f5147bd2b --- /dev/null +++ b/fs/btrfs/ulist.c @@ -0,0 +1,220 @@ +/* + * Copyright (C) 2011 STRATO AG + * written by Arne Jansen <sensille@gmx.net> + * Distributed under the GNU GPL license version 2. + */ + +#include <linux/slab.h> +#include <linux/module.h> +#include "ulist.h" + +/* + * ulist is a generic data structure to hold a collection of unique u64 + * values. The only operations it supports is adding to the list and + * enumerating it. + * It is possible to store an auxiliary value along with the key. + * + * The implementation is preliminary and can probably be sped up + * significantly. A first step would be to store the values in an rbtree + * as soon as ULIST_SIZE is exceeded. + * + * A sample usage for ulists is the enumeration of directed graphs without + * visiting a node twice. The pseudo-code could look like this: + * + * ulist = ulist_alloc(); + * ulist_add(ulist, root); + * elem = NULL; + * + * while ((elem = ulist_next(ulist, elem)) { + * for (all child nodes n in elem) + * ulist_add(ulist, n); + * do something useful with the node; + * } + * ulist_free(ulist); + * + * This assumes the graph nodes are adressable by u64. This stems from the + * usage for tree enumeration in btrfs, where the logical addresses are + * 64 bit. + * + * It is also useful for tree enumeration which could be done elegantly + * recursively, but is not possible due to kernel stack limitations. The + * loop would be similar to the above. + */ + +/** + * ulist_init - freshly initialize a ulist + * @ulist: the ulist to initialize + * + * Note: don't use this function to init an already used ulist, use + * ulist_reinit instead. + */ +void ulist_init(struct ulist *ulist) +{ + ulist->nnodes = 0; + ulist->nodes = ulist->int_nodes; + ulist->nodes_alloced = ULIST_SIZE; +} +EXPORT_SYMBOL(ulist_init); + +/** + * ulist_fini - free up additionally allocated memory for the ulist + * @ulist: the ulist from which to free the additional memory + * + * This is useful in cases where the base 'struct ulist' has been statically + * allocated. + */ +void ulist_fini(struct ulist *ulist) +{ + /* + * The first ULIST_SIZE elements are stored inline in struct ulist. + * Only if more elements are alocated they need to be freed. + */ + if (ulist->nodes_alloced > ULIST_SIZE) + kfree(ulist->nodes); + ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */ +} +EXPORT_SYMBOL(ulist_fini); + +/** + * ulist_reinit - prepare a ulist for reuse + * @ulist: ulist to be reused + * + * Free up all additional memory allocated for the list elements and reinit + * the ulist. + */ +void ulist_reinit(struct ulist *ulist) +{ + ulist_fini(ulist); + ulist_init(ulist); +} +EXPORT_SYMBOL(ulist_reinit); + +/** + * ulist_alloc - dynamically allocate a ulist + * @gfp_mask: allocation flags to for base allocation + * + * The allocated ulist will be returned in an initialized state. + */ +struct ulist *ulist_alloc(unsigned long gfp_mask) +{ + struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask); + + if (!ulist) + return NULL; + + ulist_init(ulist); + + return ulist; +} +EXPORT_SYMBOL(ulist_alloc); + +/** + * ulist_free - free dynamically allocated ulist + * @ulist: ulist to free + * + * It is not necessary to call ulist_fini before. + */ +void ulist_free(struct ulist *ulist) +{ + if (!ulist) + return; + ulist_fini(ulist); + kfree(ulist); +} +EXPORT_SYMBOL(ulist_free); + +/** + * ulist_add - add an element to the ulist + * @ulist: ulist to add the element to + * @val: value to add to ulist + * @aux: auxiliary value to store along with val + * @gfp_mask: flags to use for allocation + * + * Note: locking must be provided by the caller. In case of rwlocks write + * locking is needed + * + * Add an element to a ulist. The @val will only be added if it doesn't + * already exist. If it is added, the auxiliary value @aux is stored along with + * it. In case @val already exists in the ulist, @aux is ignored, even if + * it differs from the already stored value. + * + * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been + * inserted. + * In case of allocation failure -ENOMEM is returned and the ulist stays + * unaltered. + */ +int ulist_add(struct ulist *ulist, u64 val, unsigned long aux, + unsigned long gfp_mask) +{ + int i; + + for (i = 0; i < ulist->nnodes; ++i) { + if (ulist->nodes[i].val == val) + return 0; + } + + if (ulist->nnodes >= ulist->nodes_alloced) { + u64 new_alloced = ulist->nodes_alloced + 128; + struct ulist_node *new_nodes; + void *old = NULL; + + /* + * if nodes_alloced == ULIST_SIZE no memory has been allocated + * yet, so pass NULL to krealloc + */ + if (ulist->nodes_alloced > ULIST_SIZE) + old = ulist->nodes; + + new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced, + gfp_mask); + if (!new_nodes) + return -ENOMEM; + + if (!old) + memcpy(new_nodes, ulist->int_nodes, + sizeof(ulist->int_nodes)); + + ulist->nodes = new_nodes; + ulist->nodes_alloced = new_alloced; + } + ulist->nodes[ulist->nnodes].val = val; + ulist->nodes[ulist->nnodes].aux = aux; + ++ulist->nnodes; + + return 1; +} +EXPORT_SYMBOL(ulist_add); + +/** + * ulist_next - iterate ulist + * @ulist: ulist to iterate + * @prev: previously returned element or %NULL to start iteration + * + * Note: locking must be provided by the caller. In case of rwlocks only read + * locking is needed + * + * This function is used to iterate an ulist. The iteration is started with + * @prev = %NULL. It returns the next element from the ulist or %NULL when the + * end is reached. No guarantee is made with respect to the order in which + * the elements are returned. They might neither be returned in order of + * addition nor in ascending order. + * It is allowed to call ulist_add during an enumeration. Newly added items + * are guaranteed to show up in the running enumeration. + */ +struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_node *prev) +{ + int next; + + if (ulist->nnodes == 0) + return NULL; + + if (!prev) + return &ulist->nodes[0]; + + next = (prev - ulist->nodes) + 1; + if (next < 0 || next >= ulist->nnodes) + return NULL; + + return &ulist->nodes[next]; +} +EXPORT_SYMBOL(ulist_next); diff --git a/fs/btrfs/ulist.h b/fs/btrfs/ulist.h new file mode 100644 index 00000000000..2e25dec58ec --- /dev/null +++ b/fs/btrfs/ulist.h @@ -0,0 +1,68 @@ +/* + * Copyright (C) 2011 STRATO AG + * written by Arne Jansen <sensille@gmx.net> + * Distributed under the GNU GPL license version 2. + * + */ + +#ifndef __ULIST__ +#define __ULIST__ + +/* + * ulist is a generic data structure to hold a collection of unique u64 + * values. The only operations it supports is adding to the list and + * enumerating it. + * It is possible to store an auxiliary value along with the key. + * + * The implementation is preliminary and can probably be sped up + * significantly. A first step would be to store the values in an rbtree + * as soon as ULIST_SIZE is exceeded. + */ + +/* + * number of elements statically allocated inside struct ulist + */ +#define ULIST_SIZE 16 + +/* + * element of the list + */ +struct ulist_node { + u64 val; /* value to store */ + unsigned long aux; /* auxiliary value saved along with the val */ +}; + +struct ulist { + /* + * number of elements stored in list + */ + unsigned long nnodes; + + /* + * number of nodes we already have room for + */ + unsigned long nodes_alloced; + + /* + * pointer to the array storing the elements. The first ULIST_SIZE + * elements are stored inline. In this case the it points to int_nodes. + * After exceeding ULIST_SIZE, dynamic memory is allocated. + */ + struct ulist_node *nodes; + + /* + * inline storage space for the first ULIST_SIZE entries + */ + struct ulist_node int_nodes[ULIST_SIZE]; +}; + +void ulist_init(struct ulist *ulist); +void ulist_fini(struct ulist *ulist); +void ulist_reinit(struct ulist *ulist); +struct ulist *ulist_alloc(unsigned long gfp_mask); +void ulist_free(struct ulist *ulist); +int ulist_add(struct ulist *ulist, u64 val, unsigned long aux, + unsigned long gfp_mask); +struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_node *prev); + +#endif |