From: Shachar Sharon <synarete@gmail.com>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, eblake@redhat.com,
libguestfs@redhat.com
Subject: Re: [PATCH v2] fuse: Allow fallocate(FALLOC_FL_ZERO_RANGE)
Date: Wed, 12 May 2021 17:27:22 +0300 [thread overview]
Message-ID: <YJvlyiTR7LVM4q1n@lpc> (raw)
In-Reply-To: <20210512103704.3505086-2-rjones@redhat.com>
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' ?
>A way to test this is with the following script:
>
>--------------------
> #!/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
> EOF
>
> # Fuse-mount NBD instance as a file.
> touch test.img
> nbdfuse test.img nbd://localhost & sleep 2
> ls -lh test.img
>
> # Run a read, write, trim and zero request.
> dd if=test.img of=/dev/null bs=512 skip=1024 count=1
> dd if=/dev/zero of=test.img bs=512 skip=2048 count=1
> fallocate -p -l 512 -o 4096 test.img
> fallocate -z -l 512 -o 8192 test.img
>
> # Print the output from the NBD server.
> cat $output
>
> # Clean up.
> fusermount3 -u test.img
> killall nbdkit
> rm test.img $output
> --------------------
>
>which will print:
>
> pread 4096 524288 # number depends on readahead
> pwrite 512 0
> trim 512 4096
> zero 512 8192 may_trim
>
>The last line indicates that the FALLOC_FL_ZERO_RANGE request was
>successfully passed through by the kernel module to nbdfuse,
>translated to NBD_CMD_WRITE_ZEROES and sent through to the server.
>
>Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
>---
> fs/fuse/file.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
>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));
>
> bool block_faults = FUSE_IS_DAX(inode) && lock_inode;
>
>- if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>+ if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
>+ FALLOC_FL_ZERO_RANGE))
> return -EOPNOTSUPP;
>
> if (fm->fc->no_fallocate)
>@@ -2926,7 +2928,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
> goto out;
> }
>
>- if (mode & FALLOC_FL_PUNCH_HOLE) {
>+ if ((mode & FALLOC_FL_PUNCH_HOLE) ||
>+ (mode & FALLOC_FL_ZERO_RANGE)) {
> loff_t endbyte = offset + length - 1;
>
> err = fuse_writeback_range(inode, offset, endbyte);
>--
>2.31.1
>
next prev parent reply other threads:[~2021-05-12 14:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 10:37 [PATCH v2] fuse: Allow fallocate(FALLOC_FL_ZERO_RANGE) Richard W.M. Jones
2021-05-12 10:37 ` Richard W.M. Jones
2021-05-12 14:27 ` Shachar Sharon [this message]
2021-05-12 14:49 ` Richard W.M. Jones
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