On Mon, May 21, 2018 at 01:19:25PM +0800, Qu Wenruo wrote: > Although it's not that complex, but such comment could still save > several minutes for newer reader/reviewer. > > Signed-off-by: Qu Wenruo <w...@suse.com> > --- > fs/btrfs/lzo.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c > index 0667ea07f766..d0c6789ff78f 100644 > --- a/fs/btrfs/lzo.c > +++ b/fs/btrfs/lzo.c > @@ -17,6 +17,29 @@ > > #define LZO_LEN 4 > > +/* > + * Btrfs LZO compression format > + * > + * Regular LZO compressed data extent consists of: > + * 1. Header > + * Fixed size. LZO_LEN (4) bytes long, LE32. > + * Records the total size (*includes* the header) of real compressed > data. > + * > + * 2. Segment(s) > + * Variable size. Includes one segment header, and then data payload. > + * One regular LZO compressed extent can have one or more segments. > + * > + * 2.1 Segment header > + * Fixed size. LZO_LEN (4) bytes long, LE32. > + * Records the total size of the segment (*excludes* the header). > + * > + * 2.2 Data Payload > + * Variable size. Size up limit should be > lzo1x_worst_compress(PAGE_SIZE). > + * > + * While for inlined LZO compressed data extent, it doesn't have Header, just > + * *ONE* Segment.
It does have header that has the same value as the 1st segment header so it's skipped. There's also one catch in the format that if there's a less then 4 bytes left to the page size, the new segment starts on the new page. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
