On Fri, Aug 20, 2021 at 11:34:17AM +0300, Nikolay Borisov wrote: > > > On 18.08.21 г. 0:06, Omar Sandoval wrote: > > From: Omar Sandoval <osandov@xxxxxx> > > > > Currently, we only create ordered extents when ram_bytes == num_bytes > > and offset == 0. However, RWF_ENCODED writes may create extents which > > only refer to a subset of the full unencoded extent, so we need to plumb > > Can you give an example of such a case? It happens whenever we have bookend extents. Here's an easy example: $ dd if=/dev/zero of=file bs=12k count=1 1+0 records in 1+0 records out 12288 bytes (12 kB, 12 KiB) copied, 0.000202106 s, 60.8 MB/s $ sync $ truncate -s 8k file $ sync $ sudo ~/repos/osandov-linux/scripts/btrfs_map_physical ./file | column -ts$'\t' FILE OFFSET FILE SIZE EXTENT OFFSET EXTENT TYPE LOGICAL SIZE LOGICAL OFFSET PHYSICAL SIZE DEVID PHYSICAL OFFSET 0 8192 0 regular,compression=zstd 12288 217173213184 4096 1 217173213184 The decompressed data is 12k, but we only use 8k for the file.
