#ifndef HASH_H #define HASH_H /* Hash table implementation from the GIT project. */ /* Copyright 2008 (C) Linus Torvalds, GPL version 2 */ /* * These are some simple generic hash table helper functions. * Not necessarily suitable for all users, but good for things * where you want to just keep track of a list of things, and * have a good hash to use on them. * * It keeps the hash table at roughly 50-75% free, so the memory * cost of the hash table itself is roughly * * 3 * 2*sizeof(void *) * nr_of_objects * * bytes. * * FIXME: on 64-bit architectures, we waste memory. It would be * good to have just 32-bit pointers, requiring a special allocator * for hashed entries or something. */ #include #define alloc_nr(x) (((x) + 16) * 3 / 2) #define INSERT_HASH_PROTOS(ops, table) \ do { \ void **pos = insert_hash((ops).key, &(ops), &(table)); \ /* We already had an entry there? */ \ if (pos) { \ (ops).next = *pos; \ *pos = &(ops); \ } \ } while (0) struct hash_table_entry { unsigned int hash; void *ptr; }; struct hash_table { unsigned int size, nr; struct hash_table_entry *array; }; extern void *lookup_hash(unsigned int hash, const struct hash_table *table); extern void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table); extern void *remove_hash(unsigned int hash, void *ptr, void *ptr_next, struct hash_table *table); extern int for_each_hash(const struct hash_table *table, int (*fn)(void *)); extern int for_each_hash_int(const struct hash_table *table, int (*fn)(void *, int), int arg); extern void free_hash(struct hash_table *table); static inline void init_hash(struct hash_table *table) { table->size = 0; table->nr = 0; table->array = NULL; } static inline unsigned char icase_hash(unsigned char c) { return c & ~((c & 0x40) >> 1); } static inline unsigned int hash_name(const char *name, int namelen) { unsigned int hash = 0x123; do { unsigned char c = *name++; c = icase_hash(c); hash = hash * 101 + c; } while (--namelen); return hash; } #endif /* HASH_H */ -next.git/diff/?h=packet-loop-back&id=d787be4092e27728cb4c012bee9762098ef3c662'>diff
diff options
context:
space:
mode:
authorNeilBrown <neilb@suse.com>2016-06-02 16:19:53 +1000
committerShaohua Li <shli@fb.com>2016-06-13 11:54:22 -0700
commitd787be4092e27728cb4c012bee9762098ef3c662 (patch)
treeb8de57ed842d3c01f6fdd4f6ee5be6408763a993
parentf5b67ae86ee317db20c0e10d54f16a0bbbd3207d (diff)
md: reduce the number of synchronize_rcu() calls when multiple devices fail.
Every time a device is removed with ->hot_remove_disk() a synchronize_rcu() call is made which can delay several milliseconds in some case. If lots of devices fail at once - as could happen with a large RAID10 where one set of devices are removed all at once - these delays can add up to be very inconcenient. As failure is not reversible we can check for that first, setting a separate flag if it is found, and then all synchronize_rcu() once for all the flagged devices. Then ->hot_remove_disk() function can skip the synchronize_rcu() step if the flag is set. fix build error(Shaohua) Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat