On Thu, Nov 17, 2022 at 10:53 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>
> Commit 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs
> copies") removed fallback to generic_copy_file_range() for cross-fs
> cases inside vfs_copy_file_range().
>
> To preserve behavior of nfsd and ksmbd server-side-copy, the fallback to
> generic_copy_file_range() was added in nfsd and ksmbd code, but that
> call is missing sb_start_write(), fsnotify hooks and more.
>
> Ideally, nfsd and ksmbd would pass a flag to vfs_copy_file_range() that
> will take care of the fallback, but that code would be subtle and we got
> vfs_copy_file_range() logic wrong too many times already.
>
> Instead, add a flag to explicitly request vfs_copy_file_range() to
> perform only generic_copy_file_range() and let nfsd and ksmbd use this
> flag only in the fallback path.
>
> This choise keeps the logic changes to minimum in the non-nfsd/ksmbd code
> paths to reduce the risk of further regressions.
>
> Fixes: 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs copies")
> Tested-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
> Tested-by: Luis Henriques <lhenriques@xxxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
>
> Hi Linus,
>
> I've tried Al, but he seems to be AFK, so since you ended up applying
> the regressing commit, I might as well send you the fix as well.
>
> I intentionally chose a fix "for dummies", because I'd like to end this
> copy_file_range() regression streak.
>
> I ran the copy_range fstests group on ext4/xfs/overlay to verify no
> regressions in local fs and nfsv3/nfsv4 to test server-side-copy.
>
> I also patched copy_file_range() locally to test the "dumb" fallback
> code on local fs.
>
> Namje tested ksmbd.
>
> Please apply.
>
Ping.
Happy Thanksgiving!
Amir.
>
> Changes since v1:
> - Added Tested-by's
>
> fs/ksmbd/vfs.c | 6 +++---
> fs/nfsd/vfs.c | 4 ++--
> fs/read_write.c | 19 +++++++++++++++----
> include/linux/fs.h | 8 ++++++++
> 4 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
> index 8de970d6146f..94b8ed4ef870 100644
> --- a/fs/ksmbd/vfs.c
> +++ b/fs/ksmbd/vfs.c
> @@ -1794,9 +1794,9 @@ int ksmbd_vfs_copy_file_ranges(struct ksmbd_work *work,
> ret = vfs_copy_file_range(src_fp->filp, src_off,
> dst_fp->filp, dst_off, len, 0);
> if (ret == -EOPNOTSUPP || ret == -EXDEV)
> - ret = generic_copy_file_range(src_fp->filp, src_off,
> - dst_fp->filp, dst_off,
> - len, 0);
> + ret = vfs_copy_file_range(src_fp->filp, src_off,
> + dst_fp->filp, dst_off, len,
> + COPY_FILE_SPLICE);
> if (ret < 0)
> return ret;
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index f650afedd67f..5cf11cde51f8 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -596,8 +596,8 @@ ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
> ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
>
> if (ret == -EOPNOTSUPP || ret == -EXDEV)
> - ret = generic_copy_file_range(src, src_pos, dst, dst_pos,
> - count, 0);
> + ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count,
> + COPY_FILE_SPLICE);
> return ret;
> }
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 328ce8cf9a85..24b9668d6377 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1388,6 +1388,8 @@ ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> size_t len, unsigned int flags)
> {
> + lockdep_assert(sb_write_started(file_inode(file_out)->i_sb));
> +
> return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> }
> @@ -1424,7 +1426,9 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
> * and several different sets of file_operations, but they all end up
> * using the same ->copy_file_range() function pointer.
> */
> - if (file_out->f_op->copy_file_range) {
> + if (flags & COPY_FILE_SPLICE) {
> + /* cross sb splice is allowed */
> + } else if (file_out->f_op->copy_file_range) {
> if (file_in->f_op->copy_file_range !=
> file_out->f_op->copy_file_range)
> return -EXDEV;
> @@ -1474,8 +1478,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> size_t len, unsigned int flags)
> {
> ssize_t ret;
> + bool splice = flags & COPY_FILE_SPLICE;
>
> - if (flags != 0)
> + if (flags & ~COPY_FILE_SPLICE)
> return -EINVAL;
>
> ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
> @@ -1501,14 +1506,14 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> * same sb using clone, but for filesystems where both clone and copy
> * are supported (e.g. nfs,cifs), we only call the copy method.
> */
> - if (file_out->f_op->copy_file_range) {
> + if (!splice && file_out->f_op->copy_file_range) {
> ret = file_out->f_op->copy_file_range(file_in, pos_in,
> file_out, pos_out,
> len, flags);
> goto done;
> }
>
> - if (file_in->f_op->remap_file_range &&
> + if (!splice && file_in->f_op->remap_file_range &&
> file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {
> ret = file_in->f_op->remap_file_range(file_in, pos_in,
> file_out, pos_out,
> @@ -1528,6 +1533,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> * consistent story about which filesystems support copy_file_range()
> * and which filesystems do not, that will allow userspace tools to
> * make consistent desicions w.r.t using copy_file_range().
> + *
> + * We also get here if caller (e.g. nfsd) requested COPY_FILE_SPLICE.
> */
> ret = generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
> flags);
> @@ -1582,6 +1589,10 @@ SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in,
> pos_out = f_out.file->f_pos;
> }
>
> + ret = -EINVAL;
> + if (flags != 0)
> + goto out;
> +
> ret = vfs_copy_file_range(f_in.file, pos_in, f_out.file, pos_out, len,
> flags);
> if (ret > 0) {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f1651..59ae95ddb679 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2089,6 +2089,14 @@ struct dir_context {
> */
> #define REMAP_FILE_ADVISORY (REMAP_FILE_CAN_SHORTEN)
>
> +/*
> + * These flags control the behavior of vfs_copy_file_range().
> + * They are not available to the user via syscall.
> + *
> + * COPY_FILE_SPLICE: call splice direct instead of fs clone/copy ops
> + */
> +#define COPY_FILE_SPLICE (1 << 0)
> +
> struct iov_iter;
> struct io_uring_cmd;
>
> --
> 2.25.1
>
