Discussion:
[PATCH] btrfs-progs: fix dev stats error output related to replace handle
(too old to reply)
Gui Hecheng
2014-10-23 01:56:11 UTC
Permalink
Steps to reproduce:
# mkfs.btrfs -f /dev/sdb7
# mount /dev/sdb7 /mnt
# btrfs dev stats /dev/sdb7
output:
[/dev/sdb7].write_io_errs 0
[/dev/sdb7].read_io_errs 0
[/dev/sdb7].flush_io_errs 0
[/dev/sdb7].corruption_errs 0
[/dev/sdb7].generation_errs 0
* ERROR: ioctl(BTRFS_IOC_GET_DEV_STATS) on failed: No such device

while the following cmd:
# btrfs dev stats /mnt
yields the right thing:
[/dev/sdb7].write_io_errs 0
[/dev/sdb7].read_io_errs 0
[/dev/sdb7].flush_io_errs 0
[/dev/sdb7].corruption_errs 0
[/dev/sdb7].generation_errs 0

This is caused by commit:
commit d0588bfa479409b2a0f6243f894338a01a56221a
btrfs-progs: do a separate probe for transient replacing device

The above commit trys to handle the fi show problem with device under
replacing, but it changes the @get_fs_info() logic which annoys dev stats.
For @get_fs_info():
o If the passed in @path is a mount point, then the @get_device_info() to
probe the replacing device will be glad to accept the device index
var @i as its init value 0 and the following i++ correctly sets @i
to 1 as the start of all devices in btrfs.
o If @path is a block device, then the problem comes...
The device index @i is set to devid of the block device passed in,
and the @get_device_info() will be forced to accept the devid unwillingly.
Then the following i++ do the evil of skip the block device desired and an
empty piece is handled next which causes the ERROR above.

To fix this problem, let's just pass 0 to the @get_device_info() explicitly,
and set the index @i to 1 if a mount point is passed in.

Under my own test, this will not affect the original fix of the fi show
problem with device under replacing.

Signed-off-by: Gui Hecheng <***@cn.fujitsu.com>
---
utils.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/utils.c b/utils.c
index f10c178..0ba2b26 100644
--- a/utils.c
+++ b/utils.c
@@ -1881,12 +1881,15 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
}

/* get the replace target device if it is there */
- ret = get_device_info(fd, i, &di_args[ndevs]);
+ ret = get_device_info(fd, 0, &di_args[ndevs]);
if (!ret) {
ndevs++;
fi_args->num_devices++;
}
- i++;
+
+ /* if a mount point is passed in, start from devid 1 */
+ if (fi_args->num_devices != 1)
+ i = 1;

for (; i <= fi_args->max_id; ++i) {
BUG_ON(ndevs >= fi_args->num_devices);
--
1.8.1.4

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