vfs: fix copy_file_range() averts filesystem freeze protection

commit 10bc8e4af65946b727728d7479c028742321b60a upstream.

[backport comments for pre v5.15:
- ksmbd mentions are irrelevant - ksmbd hunks were dropped
- sb_write_started() is missing - assert was dropped
]

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@kernel.org>
Tested-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 745f0663b5b64683187d4c1cce1c6f124445dee1..b09ead06a2490265a9ac32523af4df58b37d2db9 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -584,8 +584,8 @@ 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 68604b3c3994b2d6302ffea39538ad67808496dc..0066acb6b380d125228417730c9f2b6a90679373 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1419,7 +1419,9 @@ 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;
@@ -1469,8 +1471,9 @@ 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,
@@ -1496,14 +1499,14 @@ 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,
@@ -1523,6 +1526,8 @@ 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);
@@ -1577,6 +1582,10 @@ 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 df54acdd355495fe144be5dcfc1dff0887586bf8..ebfc0b2b4969eb81262f2e347851e79a98b55bf0 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1817,6 +1817,14 @@ 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 file_operations {