btrfs: allow setting zlib compression level via :9
This is bikeshedding, but it seems people are drastically more likely to
understand "zlib:9" as compression level rather than an algorithm
version compared to "zlib9".
Based on feedback on the mailinglist, the ":9" will be the only accepted
syntax. The level must be a single digit. Unrecognized format will
result to the default, for forward compatibility in a similar way the
compression algorithm specifier was relaxed in commit
a7164fa4e055daf6368c ("btrfs: prepare for extensions in compression
options").
Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Reviewed-by: David Sterba <dsterba@suse.com>
[ tighten the accepted format ]
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 3e45252..083f9c4 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1111,8 +1111,9 @@ unsigned int btrfs_compress_str2level(const char *str)
if (strncmp(str, "zlib", 4) != 0)
return 0;
- if ('1' <= str[4] && str[4] <= '9' )
- return str[4] - '0';
+ /* Accepted form: zlib:1 up to zlib:9 and nothing left after the number */
+ if (str[4] == ':' && '1' <= str[5] && str[5] <= '9' && str[6] == 0)
+ return str[5] - '0';
return 0;
}