copy_file_range: fix fallback when source create on same txg

In 019dea0a5 we removed the conversion from EAGAIN->EXDEV inside
zfs_clone_range(), but forgot to add a test for EAGAIN to the
copy_file_range() entry points to trigger fallback to a content copy.

This commit fixes that.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Kay Pedersen <mail@mkwg.de>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #15170
Closes #15172

module/os/freebsd/zfs/zfs_vnops_os.c

@@ -6290,7 +6290,8 @@ zfs_freebsd_copy_file_range(struct vop_copy_file_range_args *ap)
 
 	error = zfs_clone_range(VTOZ(invp), ap->a_inoffp, VTOZ(outvp),
 	    ap->a_outoffp, &len, ap->a_outcred);
-	if (error == EXDEV || error == EINVAL || error == EOPNOTSUPP)
+	if (error == EXDEV || error == EAGAIN || error == EINVAL ||
+	    error == EOPNOTSUPP)
 		goto bad_locked_fallback;
 	*ap->a_lenp = (size_t)len;
 out_locked:

module/os/linux/zfs/zpl_file_range.c

@@ -103,7 +103,8 @@ zpl_copy_file_range(struct file *src_file, loff_t src_off,
 	 * Since Linux 5.3 the filesystem driver is responsible for executing
 	 * an appropriate fallback, and a generic fallback function is provided.
 	 */
-	if (ret == -EOPNOTSUPP || ret == -EINVAL || ret == -EXDEV)
+	if (ret == -EOPNOTSUPP || ret == -EINVAL || ret == -EXDEV ||
+	    ret == -EAGAIN)
 		ret = generic_copy_file_range(src_file, src_off, dst_file,
 		    dst_off, len, flags);
 #else
@@ -111,7 +112,7 @@ zpl_copy_file_range(struct file *src_file, loff_t src_off,
 	 * Before Linux 5.3 the filesystem has to return -EOPNOTSUPP to signal
 	 * to the kernel that it should fallback to a content copy.
 	 */
-	if (ret == -EINVAL || ret == -EXDEV)
+	if (ret == -EINVAL || ret == -EXDEV || ret == -EAGAIN)
 		ret = -EOPNOTSUPP;
 #endif /* HAVE_VFS_GENERIC_COPY_FILE_RANGE */
 

module/zfs/zfs_vnops.c

@@ -1246,9 +1246,10 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
 		    &nbps);
 		if (error != 0) {
 			/*
-			 * If we are tyring to clone a block that was created
-			 * in the current transaction group. Return an error,
-			 * so the caller can fallback to just copying the data.
+			 * If we are trying to clone a block that was created
+			 * in the current transaction group, error will be
+			 * EAGAIN here, which we can just return to the caller
+			 * so it can fallback if it likes.
 			 */
 			break;
 		}