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Commit d48458d4 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

jbd2: use a better hash function for the revoke table 



The old hash function didn't work well for 64-bit block numbers, and
used undefined (negative) shift right behavior.  Use the generic
64-bit hash function instead.

Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reported-by: default avatarAndrey Ryabinin <a.ryabinin@samsung.com>
parent a41537e6

fs/jbd2/revoke.c

+2 −8
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ 
#include <linux/init.h>

#include <linux/bio.h>

#include <linux/log2.h>

#include <linux/hash.h>

#endif



static struct kmem_cache *jbd2_revoke_record_cache;
@@ -130,16 +131,9 @@ static void flush_descriptor(journal_t *, struct buffer_head *, int, int); 


/* Utility functions to maintain the revoke table */



/* Borrowed from buffer.c: this is a tried and tested block hash function */

static inline int hash(journal_t *journal, unsigned long long block)

{

	struct jbd2_revoke_table_s *table = journal->j_revoke;

	int hash_shift = table->hash_shift;

	int hash = (int)block ^ (int)((block >> 31) >> 1);



	return ((hash << (hash_shift - 6)) ^

		(hash >> 13) ^

		(hash << (hash_shift - 12))) & (table->hash_size - 1);

	return hash_64(block, journal->j_revoke->hash_shift);

}



static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,