[Drbd-dev] [PATCH] drbdmeta: Fix drbdmeta to support old kernels

[Artem Pogartsev]

Hello,

RedHat 6.9
kernel-2.6.32-431.11.2
drbd-utils-9.0.0
drbd-8.4.10

Problem:

drbdmeta 0 v08 /dev/sda internal create-md
initializing activity log
initializing bitmap (30524 KB) to all zero
ioctl(/dev/sda) failed: Invalid argument

Reason:

Wrong check of the return error code into zeroout_bitmap function 
(user/shared/drbdmeta.c):

err = ioctl(cfg->md_fd, BLKZEROOUT, &range);
if (!err)
         return;
if (errno == ENOTTY) {
         do pwrite stuff;
}

We must check if errno == EINVAL (request code or argp is not valid). We 
will get ENOTTY if the block device doesnt has ioctl into fops structure 
(look at the __blkdev_driver_ioctl into block/ioctl.c) - not out case. 
And we will get EINVAL if the request code is wrong for this type of the 
device (old kernels doesnt have BLKZEROOUT) - our case.

Possible patch is attached.

But maybe better change logic and make ioctl with BLKZEROOUT only if 
BLKZEROOUT was defined in kernel headers (if we dont have BLKZEROOUT 
macro in kernel tree then 100% ioctl with _IO(0x12,127) will fail).

-------------- next part --------------
diff -Nru a/user/shared/drbdmeta.c b/user/shared/drbdmeta.c
--- a/user/shared/drbdmeta.c	2017-04-20 10:35:02.000000000 +0300
+++ b/user/shared/drbdmeta.c	2017-08-17 04:26:35.509000784 +0300
@@ -1716,7 +1716,7 @@
 	if (!err)
 		return;
 
-	if (errno == ENOTTY) {
+	if (errno == EINVAL) {
 		/* need to sector-align this for O_DIRECT.
 		 * "sector" here means hard-sect size, which may be != 512.
 		 * Note that even though ALIGN does round up, for sector sizes