On Wed, May 12, 2021 at 05:27:22PM +0300, Shachar Sharon wrote: > On Wed, May 12, 2021 at 11:37:04AM +0100, Richard W.M. Jones wrote: > >libnbd's nbdfuse utility would like to translate fallocate zero > >requests into NBD_CMD_WRITE_ZEROES. Currently the fuse module filters > >these out, returning -EOPNOTSUPP. This commit treats these almost the > >same way as FALLOC_FL_PUNCH_HOLE except not calling > >truncate_pagecache_range. > > > Why don't you call 'truncate_pagecache_range' ? Very good point. I just assumed that it would only be useful when hole-punching, but now I actually read the description of the function I see we need it. Also looking at other filesystems that also support FALLOC_FL_ZERO_RANGE: ext4_zero_range -> calls truncate_pagecache_range f2fs_zero_range -> calls it xfs -> calls it indirectly btrfs_zero_range -> does not call it (?) I'll add this, and retest everything. > >A way to test this is with the following script: In my next version I'll also address this script which is rather long-winded. I think there's an easier way for people to test this: > >-------------------- > > #!/bin/bash > > # Requires fuse >= 3, nbdkit >= 1.8, and latest nbdfuse from > > # https://gitlab.com/nbdkit/libnbd/-/tree/master/fuse > > set -e > > set -x > > > > export output=$PWD/output > > rm -f test.img $output > > > > # Create an nbdkit instance that prints the NBD requests seen. > > nbdkit sh - <<'EOF' > > case "$1" in > > get_size) echo 1M ;; > > can_write|can_trim|can_zero|can_fast_zero) ;; > > pread) echo "$@" >>$output; dd if=/dev/zero count=$3 iflag=count_bytes ;; > > pwrite) echo "$@" >>$output; cat >/dev/null ;; > > trim|zero) echo "$@" >>$output ;; > > *) exit 2 ;; > > esac [etc] > >diff --git a/fs/fuse/file.c b/fs/fuse/file.c > >index 09ef2a4d25ed..22e8e88c78d4 100644 > >--- a/fs/fuse/file.c > >+++ b/fs/fuse/file.c > >@@ -2907,11 +2907,13 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > > }; > > int err; > > bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) || > >- (mode & FALLOC_FL_PUNCH_HOLE); > >+ (mode & FALLOC_FL_PUNCH_HOLE) || > >+ (mode & FALLOC_FL_ZERO_RANGE); > To stay aligned with existing code style, consider: > - (mode & FALLOC_FL_PUNCH_HOLE); > +» » » (mode & (FALLOC_FL_PUNCH_HOLE | > +» » » » FALLOC_FL_ZERO_RANGE)); Good idea. Thanks for the quick review. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org
