CVSROOT: /cvs
Module name: src
Changes by: s...@cvs.openbsd.org 2016/08/30 13:47:23
Modified files:
sys/msdosfs : denode.h msdosfs_vnops.c
Log message:
Revert "Implement VFS read clustering for MSDOSFS"
This caused garbage to be written instead of blocks of 0-bytes if a
file is extended by seeking past the end. This happens for example
when extracting files containing lots of 0-bytes with tar.
ok mpi@
Details of original commit:
msdosfs_vnops.c revision 1.105
denode.h revision 1.28
date: 2016/01/13 10:00:55; author: mpi; commitid: ru9jHQwQX09BC5Bw;
Implement VFS read clustering for MSDOSFS.
The logic used in msdosfs_bmap() to loop calling pcbmap() comes from
FreeBSD and is not really efficient but it is good enough since it is
only called when generating I/O.
With this diff I get a 100% improvement when reading big files from a
crappy USB stick.
With this and bread_cluster(9) modified to not re-fetch B_CACHED buffers,
reading large contiguous files with chunk sizes of MAXPHYS is almost as
fast as physio(9) on the same device.
For a 'real world' example, when copying music files from a USB stick I
see a speed jump from 15MB/s on -current to 24Mb/s with this diff.
While here rename some 'lbn' variables into 'cn' to better reflect what
we're dealing with.
Tested by Mathieu, with support from deraadt@
