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author | David Howells <dhowells@redhat.com> | 2021-06-17 16:21:00 +0300 |
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committer | David Howells <dhowells@redhat.com> | 2021-08-27 15:34:02 +0300 |
commit | 35b72573e977ed6b18b094136a4fa3e0ffb13603 (patch) | |
tree | b297cf2571e9b264199825f0cd140acf7733e624 /fs/fscache/cookie.c | |
parent | 8beabdde18d31ac10c7d211347c361f07c7cd5b0 (diff) | |
download | linux-35b72573e977ed6b18b094136a4fa3e0ffb13603.tar.xz |
fscache: Fix cookie key hashing
The current hash algorithm used for hashing cookie keys is really bad,
producing almost no dispersion (after a test kernel build, ~30000 files
were split over just 18 out of the 32768 hash buckets).
Borrow the full_name_hash() hash function into fscache to do the hashing
for cookie keys and, in the future, volume keys.
I don't want to use full_name_hash() as-is because I want the hash value to
be consistent across arches and over time as the hash value produced may
get used on disk.
I can also optimise parts of it away as the key will always be a padded
array of aligned 32-bit words.
Fixes: ec0328e46d6e ("fscache: Maintain a catalogue of allocated cookies")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/162431201844.2908479.8293647220901514696.stgit@warthog.procyon.org.uk/
Diffstat (limited to 'fs/fscache/cookie.c')
-rw-r--r-- | fs/fscache/cookie.c | 14 |
1 files changed, 1 insertions, 13 deletions
diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index ec9bce33085f..2558814193e9 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -87,10 +87,8 @@ void fscache_free_cookie(struct fscache_cookie *cookie) static int fscache_set_key(struct fscache_cookie *cookie, const void *index_key, size_t index_key_len) { - unsigned long long h; u32 *buf; int bufs; - int i; bufs = DIV_ROUND_UP(index_key_len, sizeof(*buf)); @@ -104,17 +102,7 @@ static int fscache_set_key(struct fscache_cookie *cookie, } memcpy(buf, index_key, index_key_len); - - /* Calculate a hash and combine this with the length in the first word - * or first half word - */ - h = (unsigned long)cookie->parent; - h += index_key_len + cookie->type; - - for (i = 0; i < bufs; i++) - h += buf[i]; - - cookie->key_hash = h ^ (h >> 32); + cookie->key_hash = fscache_hash(0, buf, bufs); return 0; } |