fs, jbd: use a more generic hash function

While the hash function used by the revoke hashtable is good somewhere else, it's not really good here. The default hash shift (8) means that one third of the hashing function gets lost (and is undefined anyways (8 - 12 = negative shift)): "(block << (hash_shift - 12))) & (table->hash_size - 1)" Instead, just use the kernel's generic hash function that gets used everywhere else.

Sasha Levin committed 12 years ago

Commit 3c9cafe1 parent 474d2601 file · +2 −5Browse files

Unified · Split

fs/jbd/revoke.c+2−5

@@ -93,6 +93,7 @@ · 92 unmodified lines
93	93	#include <linux/bio.h>
94	94	#endif
95	95	#include <linux/log2.h>
	96	+#include <linux/hash.h>
96	97
97	98	static struct kmem_cache *revoke_record_cache;
98	99	static struct kmem_cache *revoke_table_cache;
@@ -129,15 +130,11 @@ static void flush_descriptor(journal_t , struct journal_head , int, int); · 30 unmodified lines
129	130
130	131	/* Utility functions to maintain the revoke table */
131	132
132		−/* Borrowed from buffer.c: this is a tried and tested block hash function */
133	133	static inline int hash(journal_t *journal, unsigned int block)
134	134	{
135	135	struct jbd_revoke_table_s *table = journal->j_revoke;
136		− int hash_shift = table->hash_shift;
137	136
138		− return ((block << (hash_shift - 6)) ^
139		− (block >> 13) ^
140		− (block << (hash_shift - 12))) & (table->hash_size - 1);
	137	+ return hash_32(block, table->hash_shift);
141	138	}
142	139
143	140	static int insert_revoke_hash(journal_t *journal, unsigned int blocknr,