On Wed, Aug 06, 2025 at 10:17:06AM +0100, Luis Henriques wrote: > On Tue, Aug 05 2025, Miklos Szeredi wrote: > > > The FUSE protocol uses struct fuse_write_out to convey the return value of > > copy_file_range, which is restricted to uint32_t. But the COPY_FILE_RANGE > > interface supports a 64-bit size copies. > > > > Currently the number of bytes copied is silently truncated to 32-bit, which > > is unfortunate at best. > > > > Introduce a new op COPY_FILE_RANGE_64, which is identical, except the > > number of bytes copied is returned in a 64-bit value. > > > > If the fuse server does not support COPY_FILE_RANGE_64, fall back to > > COPY_FILE_RANGE and truncate the size to UINT_MAX - 4096. > > I was wondering if it wouldn't make more sense to truncate the size to > MAX_RW_COUNT instead. My reasoning is that, if I understand the code > correctly (which is probably a big 'if'!), the VFS will fallback to > splice() if the file system does not implement copy_file_range. And in > this case splice() seems to limit the operation to MAX_RW_COUNT. It doesn't, because copy_file_range implementations can do other things (like remapping/reflinking file blocks) that produce a very small amount of disk IO for what is effectively a very large change to file contents. That's why the VFS doesn't cap len at MAX_RW_COUNT bytes. --D > Cheers, > -- > Luís > > > > Reported-by: Florian Weimer <fweimer@xxxxxxxxxx> > > Closes: https://lore.kernel.org/all/lhuh5ynl8z5.fsf@xxxxxxxxxxxxxxxxxxxxxxxx/ > > Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> > > --- > > fs/fuse/file.c | 34 ++++++++++++++++++++++++++-------- > > fs/fuse/fuse_i.h | 3 +++ > > include/uapi/linux/fuse.h | 12 +++++++++++- > > 3 files changed, 40 insertions(+), 9 deletions(-) > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > index adc4aa6810f5..bd6624885855 100644 > > --- a/fs/fuse/file.c > > +++ b/fs/fuse/file.c > > @@ -3017,6 +3017,8 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in, > > .flags = flags > > }; > > struct fuse_write_out outarg; > > + struct fuse_copy_file_range_out outarg_64; > > + u64 bytes_copied; > > ssize_t err; > > /* mark unstable when write-back is not used, and file_out gets > > * extended */ > > @@ -3066,30 +3068,46 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in, > > if (is_unstable) > > set_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state); > > > > - args.opcode = FUSE_COPY_FILE_RANGE; > > + args.opcode = FUSE_COPY_FILE_RANGE_64; > > args.nodeid = ff_in->nodeid; > > args.in_numargs = 1; > > args.in_args[0].size = sizeof(inarg); > > args.in_args[0].value = &inarg; > > args.out_numargs = 1; > > - args.out_args[0].size = sizeof(outarg); > > - args.out_args[0].value = &outarg; > > + args.out_args[0].size = sizeof(outarg_64); > > + args.out_args[0].value = &outarg_64; > > + if (fc->no_copy_file_range_64) { > > +fallback: > > + /* Fall back to old op that can't handle large copy length */ > > + args.opcode = FUSE_COPY_FILE_RANGE; > > + args.out_args[0].size = sizeof(outarg); > > + args.out_args[0].value = &outarg; > > + inarg.len = min_t(size_t, len, 0xfffff000); > > + } > > err = fuse_simple_request(fm, &args); > > if (err == -ENOSYS) { > > - fc->no_copy_file_range = 1; > > - err = -EOPNOTSUPP; > > + if (fc->no_copy_file_range_64) { > > + fc->no_copy_file_range = 1; > > + err = -EOPNOTSUPP; > > + } else { > > + fc->no_copy_file_range_64 = 1; > > + goto fallback; > > + } > > } > > if (err) > > goto out; > > > > + bytes_copied = fc->no_copy_file_range_64 ? > > + outarg.size : outarg_64.bytes_copied; > > + > > truncate_inode_pages_range(inode_out->i_mapping, > > ALIGN_DOWN(pos_out, PAGE_SIZE), > > - ALIGN(pos_out + outarg.size, PAGE_SIZE) - 1); > > + ALIGN(pos_out + bytes_copied, PAGE_SIZE) - 1); > > > > file_update_time(file_out); > > - fuse_write_update_attr(inode_out, pos_out + outarg.size, outarg.size); > > + fuse_write_update_attr(inode_out, pos_out + bytes_copied, bytes_copied); > > > > - err = outarg.size; > > + err = bytes_copied; > > out: > > if (is_unstable) > > clear_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state); > > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > > index b54f4f57789f..a8be19f686b1 100644 > > --- a/fs/fuse/fuse_i.h > > +++ b/fs/fuse/fuse_i.h > > @@ -850,6 +850,9 @@ struct fuse_conn { > > /** Does the filesystem support copy_file_range? */ > > unsigned no_copy_file_range:1; > > > > + /** Does the filesystem support copy_file_range_64? */ > > + unsigned no_copy_file_range_64:1; > > + > > /* Send DESTROY request */ > > unsigned int destroy:1; > > > > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h > > index 122d6586e8d4..94621f68a5cc 100644 > > --- a/include/uapi/linux/fuse.h > > +++ b/include/uapi/linux/fuse.h > > @@ -235,6 +235,10 @@ > > * > > * 7.44 > > * - add FUSE_NOTIFY_INC_EPOCH > > + * > > + * 7.45 > > + * - add FUSE_COPY_FILE_RANGE_64 > > + * - add struct fuse_copy_file_range_out > > */ > > > > #ifndef _LINUX_FUSE_H > > @@ -270,7 +274,7 @@ > > #define FUSE_KERNEL_VERSION 7 > > > > /** Minor version number of this interface */ > > -#define FUSE_KERNEL_MINOR_VERSION 44 > > +#define FUSE_KERNEL_MINOR_VERSION 45 > > > > /** The node ID of the root inode */ > > #define FUSE_ROOT_ID 1 > > @@ -657,6 +661,7 @@ enum fuse_opcode { > > FUSE_SYNCFS = 50, > > FUSE_TMPFILE = 51, > > FUSE_STATX = 52, > > + FUSE_COPY_FILE_RANGE_64 = 53, > > > > /* CUSE specific operations */ > > CUSE_INIT = 4096, > > @@ -1148,6 +1153,11 @@ struct fuse_copy_file_range_in { > > uint64_t flags; > > }; > > > > +/* For FUSE_COPY_FILE_RANGE_64 */ > > +struct fuse_copy_file_range_out { > > + uint64_t bytes_copied; > > +}; > > + > > #define FUSE_SETUPMAPPING_FLAG_WRITE (1ull << 0) > > #define FUSE_SETUPMAPPING_FLAG_READ (1ull << 1) > > struct fuse_setupmapping_in { > > -- > > 2.49.0 > > > >
