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| author | Timofey Titovets <nefelim4ag@gmail.com> | 2017-09-28 17:33:39 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2017-11-01 22:45:36 +0300 |
| commit | 1fe4f6fa5ae7dd1e63145e1ced7b9b38854da9f4 (patch) | |
| tree | dbe0f0b44b9814655e5b64e8b0cc72db375227b9 | |
| parent | a440d48c7f93af5bae86af676cc6cd4e9fd6015f (diff) | |
| download | linux-1fe4f6fa5ae7dd1e63145e1ced7b9b38854da9f4.tar.xz | |
Btrfs: heuristic: add detection of repeated data patterns
Walk over data sample and use memcmp to detect repeated patterns, like
zeros, but a bit more general.
Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor coding style fixes ]
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/compression.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 0e1561cc9578..0d445c815ca2 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -1222,6 +1222,14 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, return 1; } +static bool sample_repeated_patterns(struct heuristic_ws *ws) +{ + const u32 half_of_sample = ws->sample_size / 2; + const u8 *data = ws->sample; + + return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0; +} + static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end, struct heuristic_ws *ws) { @@ -1301,6 +1309,11 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) heuristic_collect_sample(inode, start, end, ws); + if (sample_repeated_patterns(ws)) { + ret = 1; + goto out; + } + memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE); for (i = 0; i < ws->sample_size; i++) { @@ -1308,8 +1321,8 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) ws->bucket[byte].count++; } +out: __free_workspace(0, ws_list, true); - return ret; } |