From: "Richard W.M. Jones" <rjones@redhat.com>
To: miklos@szeredi.hu
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
eblake@redhat.com, libguestfs@redhat.com, synarete@gmail.com
Subject: [PATCH v4] fuse: Allow fallocate(FALLOC_FL_ZERO_RANGE)
Date: Wed, 12 May 2021 17:18:48 +0100 [thread overview]
Message-ID: <20210512161848.3513818-2-rjones@redhat.com> (raw)
In-Reply-To: <20210512161848.3513818-1-rjones@redhat.com>
The current fuse module filters out fallocate(FALLOC_FL_ZERO_RANGE)
returning -EOPNOTSUPP. libnbd's nbdfuse would like to translate
FALLOC_FL_ZERO_RANGE requests into the NBD command
NBD_CMD_WRITE_ZEROES which allows NBD servers that support it to do
zeroing efficiently.
This commit treats this flag exactly like FALLOC_FL_PUNCH_HOLE.
A way to test this, requiring fuse >= 3, nbdkit >= 1.8 and the latest
nbdfuse from https://gitlab.com/nbdkit/libnbd/-/tree/master/fuse is to
create a file containing some data and "mirror" it to a fuse file:
$ dd if=/dev/urandom of=disk.img bs=1M count=1
$ nbdkit file disk.img
$ touch mirror.img
$ nbdfuse mirror.img nbd://localhost &
(mirror.img -> nbdfuse -> NBD over loopback -> nbdkit -> disk.img)
You can then run commands such as:
$ fallocate -z -o 1024 -l 1024 mirror.img
and check that the content of the original file ("disk.img") stays
synchronized. To show NBD commands, export LIBNBD_DEBUG=1 before
running nbdfuse. To clean up:
$ fusermount3 -u mirror.img
$ killall nbdkit
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
fs/fuse/file.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 09ef2a4d25ed..ec20a1801c1b 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 |
+ 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 +2928,7 @@ 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 | FALLOC_FL_ZERO_RANGE)) {
loff_t endbyte = offset + length - 1;
err = fuse_writeback_range(inode, offset, endbyte);
@@ -2966,7 +2968,7 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
file_update_time(file);
}
- if (mode & FALLOC_FL_PUNCH_HOLE)
+ if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
truncate_pagecache_range(inode, offset, offset + length - 1);
fuse_invalidate_attr(inode);
--
2.31.1
next prev parent reply other threads:[~2021-05-12 16:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 16:18 [PATCH v4] fuse: Allow fallocate(FALLOC_FL_ZERO_RANGE) Richard W.M. Jones
2021-05-12 16:18 ` Richard W.M. Jones [this message]
2021-05-18 13:56 ` Miklos Szeredi
2021-06-15 10:33 ` Richard W.M. Jones
2021-06-18 7:12 ` Miklos Szeredi
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