ceph: support copy_file_range file operation

This commit implements support for the copy_file_range syscall in cephfs.
It is implemented using the RADOS 'copy-from' operation, which allows to
do a remote object copy, without the need to download/upload data from/to
the OSDs.

Some manual copy may however be required if the source/destination file
offsets aren't object aligned or if the copy length is smaller than the
object size.
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/file.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/ceph/ceph_debug.h>
+#include <linux/ceph/striper.h>
 
 #include <linux/module.h>
 #include <linux/sched.h>
@@ -1795,6 +1796,297 @@ static long ceph_fallocate(struct file *file, int mode,
 	return ret;
 }
 
+/*
+ * This function tries to get FILE_WR capabilities for dst_ci and FILE_RD for
+ * src_ci.  Two attempts are made to obtain both caps, and an error is return if
+ * this fails; zero is returned on success.
+ */
+static int get_rd_wr_caps(struct ceph_inode_info *src_ci,
+			  loff_t src_endoff, int *src_got,
+			  struct ceph_inode_info *dst_ci,
+			  loff_t dst_endoff, int *dst_got)
+{
+	int ret = 0;
+	bool retrying = false;
+
+retry_caps:
+	ret = ceph_get_caps(dst_ci, CEPH_CAP_FILE_WR, CEPH_CAP_FILE_BUFFER,
+			    dst_endoff, dst_got, NULL);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Since we're already holding the FILE_WR capability for the dst file,
+	 * we would risk a deadlock by using ceph_get_caps.  Thus, we'll do some
+	 * retry dance instead to try to get both capabilities.
+	 */
+	ret = ceph_try_get_caps(src_ci, CEPH_CAP_FILE_RD, CEPH_CAP_FILE_SHARED,
+				false, src_got);
+	if (ret <= 0) {
+		/* Start by dropping dst_ci caps and getting src_ci caps */
+		ceph_put_cap_refs(dst_ci, *dst_got);
+		if (retrying) {
+			if (!ret)
+				/* ceph_try_get_caps masks EAGAIN */
+				ret = -EAGAIN;
+			return ret;
+		}
+		ret = ceph_get_caps(src_ci, CEPH_CAP_FILE_RD,
+				    CEPH_CAP_FILE_SHARED, src_endoff,
+				    src_got, NULL);
+		if (ret < 0)
+			return ret;
+		/*... drop src_ci caps too, and retry */
+		ceph_put_cap_refs(src_ci, *src_got);
+		retrying = true;
+		goto retry_caps;
+	}
+	return ret;
+}
+
+static void put_rd_wr_caps(struct ceph_inode_info *src_ci, int src_got,
+			   struct ceph_inode_info *dst_ci, int dst_got)
+{
+	ceph_put_cap_refs(src_ci, src_got);
+	ceph_put_cap_refs(dst_ci, dst_got);
+}
+
+/*
+ * This function does several size-related checks, returning an error if:
+ *  - source file is smaller than off+len
+ *  - destination file size is not OK (inode_newsize_ok())
+ *  - max bytes quotas is exceeded
+ */
+static int is_file_size_ok(struct inode *src_inode, struct inode *dst_inode,
+			   loff_t src_off, loff_t dst_off, size_t len)
+{
+	loff_t size, endoff;
+
+	size = i_size_read(src_inode);
+	/*
+	 * Don't copy beyond source file EOF.  Instead of simply setting length
+	 * to (size - src_off), just drop to VFS default implementation, as the
+	 * local i_size may be stale due to other clients writing to the source
+	 * inode.
+	 */
+	if (src_off + len > size) {
+		dout("Copy beyond EOF (%llu + %zu > %llu)\n",
+		     src_off, len, size);
+		return -EOPNOTSUPP;
+	}
+	size = i_size_read(dst_inode);
+
+	endoff = dst_off + len;
+	if (inode_newsize_ok(dst_inode, endoff))
+		return -EOPNOTSUPP;
+
+	if (ceph_quota_is_max_bytes_exceeded(dst_inode, endoff))
+		return -EDQUOT;
+
+	return 0;
+}
+
+static ssize_t ceph_copy_file_range(struct file *src_file, loff_t src_off,
+				    struct file *dst_file, loff_t dst_off,
+				    size_t len, unsigned int flags)
+{
+	struct inode *src_inode = file_inode(src_file);
+	struct inode *dst_inode = file_inode(dst_file);
+	struct ceph_inode_info *src_ci = ceph_inode(src_inode);
+	struct ceph_inode_info *dst_ci = ceph_inode(dst_inode);
+	struct ceph_cap_flush *prealloc_cf;
+	struct ceph_object_locator src_oloc, dst_oloc;
+	struct ceph_object_id src_oid, dst_oid;
+	loff_t endoff = 0, size;
+	ssize_t ret = -EIO;
+	u64 src_objnum, dst_objnum, src_objoff, dst_objoff;
+	u32 src_objlen, dst_objlen, object_size;
+	int src_got = 0, dst_got = 0, err, dirty;
+	bool do_final_copy = false;
+
+	if (src_inode == dst_inode)
+		return -EINVAL;
+	if (ceph_snap(dst_inode) != CEPH_NOSNAP)
+		return -EROFS;
+
+	/*
+	 * Some of the checks below will return -EOPNOTSUPP, which will force a
+	 * fallback to the default VFS copy_file_range implementation.  This is
+	 * desirable in several cases (for ex, the 'len' is smaller than the
+	 * size of the objects, or in cases where that would be more
+	 * efficient).
+	 */
+
+	if ((src_ci->i_layout.stripe_unit != dst_ci->i_layout.stripe_unit) ||
+	    (src_ci->i_layout.stripe_count != dst_ci->i_layout.stripe_count) ||
+	    (src_ci->i_layout.object_size != dst_ci->i_layout.object_size))
+		return -EOPNOTSUPP;
+
+	if (len < src_ci->i_layout.object_size)
+		return -EOPNOTSUPP; /* no remote copy will be done */
+
+	prealloc_cf = ceph_alloc_cap_flush();
+	if (!prealloc_cf)
+		return -ENOMEM;
+
+	/* Start by sync'ing the source file */
+	ret = file_write_and_wait_range(src_file, src_off, (src_off + len));
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * We need FILE_WR caps for dst_ci and FILE_RD for src_ci as other
+	 * clients may have dirty data in their caches.  And OSDs know nothing
+	 * about caps, so they can't safely do the remote object copies.
+	 */
+	err = get_rd_wr_caps(src_ci, (src_off + len), &src_got,
+			     dst_ci, (dst_off + len), &dst_got);
+	if (err < 0) {
+		dout("get_rd_wr_caps returned %d\n", err);
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	ret = is_file_size_ok(src_inode, dst_inode, src_off, dst_off, len);
+	if (ret < 0)
+		goto out_caps;
+
+	size = i_size_read(dst_inode);
+	endoff = dst_off + len;
+
+	/* Drop dst file cached pages */
+	ret = invalidate_inode_pages2_range(dst_inode->i_mapping,
+					    dst_off >> PAGE_SHIFT,
+					    endoff >> PAGE_SHIFT);
+	if (ret < 0) {
+		dout("Failed to invalidate inode pages (%zd)\n", ret);
+		ret = 0; /* XXX */
+	}
+	src_oloc.pool = src_ci->i_layout.pool_id;
+	src_oloc.pool_ns = ceph_try_get_string(src_ci->i_layout.pool_ns);
+	dst_oloc.pool = dst_ci->i_layout.pool_id;
+	dst_oloc.pool_ns = ceph_try_get_string(dst_ci->i_layout.pool_ns);
+
+	ceph_calc_file_object_mapping(&src_ci->i_layout, src_off,
+				      src_ci->i_layout.object_size,
+				      &src_objnum, &src_objoff, &src_objlen);
+	ceph_calc_file_object_mapping(&dst_ci->i_layout, dst_off,
+				      dst_ci->i_layout.object_size,
+				      &dst_objnum, &dst_objoff, &dst_objlen);
+	/* object-level offsets need to the same */
+	if (src_objoff != dst_objoff) {
+		ret = -EOPNOTSUPP;
+		goto out_caps;
+	}
+
+	/*
+	 * Do a manual copy if the object offset isn't object aligned.
+	 * 'src_objlen' contains the bytes left until the end of the object,
+	 * starting at the src_off
+	 */
+	if (src_objoff) {
+		/*
+		 * we need to temporarily drop all caps as we'll be calling
+		 * {read,write}_iter, which will get caps again.
+		 */
+		put_rd_wr_caps(src_ci, src_got, dst_ci, dst_got);
+		ret = do_splice_direct(src_file, &src_off, dst_file,
+				       &dst_off, src_objlen, flags);
+		if (ret < 0) {
+			dout("do_splice_direct returned %d\n", err);
+			goto out;
+		}
+		len -= ret;
+		err = get_rd_wr_caps(src_ci, (src_off + len),
+				     &src_got, dst_ci,
+				     (dst_off + len), &dst_got);
+		if (err < 0)
+			goto out;
+		err = is_file_size_ok(src_inode, dst_inode,
+				      src_off, dst_off, len);
+		if (err < 0)
+			goto out_caps;
+	}
+	object_size = src_ci->i_layout.object_size;
+	while (len >= object_size) {
+		ceph_calc_file_object_mapping(&src_ci->i_layout, src_off,
+					      object_size, &src_objnum,
+					      &src_objoff, &src_objlen);
+		ceph_calc_file_object_mapping(&dst_ci->i_layout, dst_off,
+					      object_size, &dst_objnum,
+					      &dst_objoff, &dst_objlen);
+		ceph_oid_init(&src_oid);
+		ceph_oid_printf(&src_oid, "%llx.%08llx",
+				src_ci->i_vino.ino, src_objnum);
+		ceph_oid_init(&dst_oid);
+		ceph_oid_printf(&dst_oid, "%llx.%08llx",
+				dst_ci->i_vino.ino, dst_objnum);
+		/* Do an object remote copy */
+		err = ceph_osdc_copy_from(
+			&ceph_inode_to_client(src_inode)->client->osdc,
+			src_ci->i_vino.snap, 0,
+			&src_oid, &src_oloc,
+			CEPH_OSD_OP_FLAG_FADVISE_SEQUENTIAL |
+			CEPH_OSD_OP_FLAG_FADVISE_NOCACHE,
+			&dst_oid, &dst_oloc,
+			CEPH_OSD_OP_FLAG_FADVISE_SEQUENTIAL |
+			CEPH_OSD_OP_FLAG_FADVISE_DONTNEED, 0);
+		if (err) {
+			dout("ceph_osdc_copy_from returned %d\n", err);
+			if (!ret)
+				ret = err;
+			goto out_caps;
+		}
+		len -= object_size;
+		src_off += object_size;
+		dst_off += object_size;
+		ret += object_size;
+	}
+
+	if (len)
+		/* We still need one final local copy */
+		do_final_copy = true;
+
+	file_update_time(dst_file);
+	if (endoff > size) {
+		int caps_flags = 0;
+
+		/* Let the MDS know about dst file size change */
+		if (ceph_quota_is_max_bytes_approaching(dst_inode, endoff))
+			caps_flags |= CHECK_CAPS_NODELAY;
+		if (ceph_inode_set_size(dst_inode, endoff))
+			caps_flags |= CHECK_CAPS_AUTHONLY;
+		if (caps_flags)
+			ceph_check_caps(dst_ci, caps_flags, NULL);
+	}
+	/* Mark Fw dirty */
+	spin_lock(&dst_ci->i_ceph_lock);
+	dst_ci->i_inline_version = CEPH_INLINE_NONE;
+	dirty = __ceph_mark_dirty_caps(dst_ci, CEPH_CAP_FILE_WR, &prealloc_cf);
+	spin_unlock(&dst_ci->i_ceph_lock);
+	if (dirty)
+		__mark_inode_dirty(dst_inode, dirty);
+
+out_caps:
+	put_rd_wr_caps(src_ci, src_got, dst_ci, dst_got);
+
+	if (do_final_copy) {
+		err = do_splice_direct(src_file, &src_off, dst_file,
+				       &dst_off, len, flags);
+		if (err < 0) {
+			dout("do_splice_direct returned %d\n", err);
+			goto out;
+		}
+		len -= err;
+		ret += err;
+	}
+
+out:
+	ceph_free_cap_flush(prealloc_cf);
+
+	return ret;
+}
+
 const struct file_operations ceph_file_fops = {
 	.open = ceph_open,
 	.release = ceph_release,
@@ -1810,5 +2102,5 @@ const struct file_operations ceph_file_fops = {
 	.unlocked_ioctl = ceph_ioctl,
 	.compat_ioctl	= ceph_ioctl,
 	.fallocate	= ceph_fallocate,
+	.copy_file_range = ceph_copy_file_range,
 };
-