On Mon, Oct 13, 2014 at 02:23:57PM +0800, Anand Jain wrote:
>
>
> comments below..
>
>
> On 10/13/14 12:42, Eryu Guan wrote:
> >device replace could fail due to another running scrub process or any
> >other errors btrfs_scrub_dev() may hit, but this failure doesn't get
> >returned to userspace.
> >
> >The following steps could reproduce this issue
> >
> > mkfs -t btrfs -f /dev/sdb1 /dev/sdb2
> > mount /dev/sdb1 /mnt/btrfs
> > while true; do btrfs scrub start -B /mnt/btrfs >/dev/null 2>&1; done &
> > btrfs replace start -Bf /dev/sdb2 /dev/sdb3 /mnt/btrfs
> > # if this replace succeeded, do the following and repeat until
> > # you see this log in dmesg
> > # BTRFS: btrfs_scrub_dev(/dev/sdb2, 2, /dev/sdb3) failed -115
> > #btrfs replace start -Bf /dev/sdb3 /dev/sdb2 /mnt/btrfs
> >
> > # once you see the error log in dmesg, check return value of
> > # replace
> > echo $?
> >
> >Introduce a new dev replace result
> >
> >BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS
> >
> >to catch -EINPROGRESS explicitly and return other errors directly to
> >userspace.
> >
> >Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
> >---
> >
> >v2:
> >- set result to SCRUB_INPROGRESS if btrfs_scrub_dev returned -EINPROGRESS
> > and return 0 as Miao Xie suggested
> >
> > fs/btrfs/dev-replace.c | 12 +++++++++---
> > include/uapi/linux/btrfs.h | 1 +
> > 2 files changed, 10 insertions(+), 3 deletions(-)
> >
> >diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> >index eea26e1..a141f8b 100644
> >--- a/fs/btrfs/dev-replace.c
> >+++ b/fs/btrfs/dev-replace.c
> >@@ -418,9 +418,15 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
> > &dev_replace->scrub_progress, 0, 1);
> >
> > ret = btrfs_dev_replace_finishing(root->fs_info, ret);
> >- WARN_ON(ret);
> >+ /* don't warn if EINPROGRESS, someone else might be running scrub */
> >+ if (ret == -EINPROGRESS) {
> >+ args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
> >+ ret = 0;
> >+ } else {
> >+ WARN_ON(ret);
> >+ }
>
>
> looks like was are trying to manage EINPROGRESS returned by
Yes, that's right.
> btrfs_dev_replace_finishing(). In btrfs_dev_replace_finishing()
> which specific func call is returning EINPROGRESS ? I didn't go
> deep enough.
btrfs_dev_replace_finishing() will check the scrub_ret(the last
argument), and return scrub_ret if (!scrub_ret). It was returning 0
unconditionally before this patch.
btrfs_dev_replace_start@fs/btrfs/dev-replace.c
416 ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
417 src_device->total_bytes,
418 &dev_replace->scrub_progress, 0, 1);
419
420 ret = btrfs_dev_replace_finishing(root->fs_info, ret);
and btrfs_dev_replace_finishing@fs/btrfs/dev-replace.c
529 if (!scrub_ret) {
530 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
531 src_device,
532 tgt_device);
533 } else {
......
547 return scrub_ret;
548 }
>
> And how do we handle if replace is intervened by balance
> instead of scrub ?
Based on my test, replace ioctl would return -ENOENT if balance is
running
ERROR: ioctl(DEV_REPLACE_START) failed on "/mnt/testarea/scratch": No such file or directory, no error
(I haven't gone through this codepath yet and don't know where -ENOENT
comes from, but I don't think it's a proper errno,
/mnt/testarea/scratch is definitely there)
>
> sorry if I missed something.
>
> Anand
Thanks for the review!
Eryu
>
>
> >- return 0;
> >+ return ret;
> >
> > leave:
> > dev_replace->srcdev = NULL;
> >@@ -538,7 +544,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
> > btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
> > mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
> >
> >- return 0;
> >+ return scrub_ret;
> > }
> >
> > printk_in_rcu(KERN_INFO
> >diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> >index 2f47824..611e1c5 100644
> >--- a/include/uapi/linux/btrfs.h
> >+++ b/include/uapi/linux/btrfs.h
> >@@ -157,6 +157,7 @@ struct btrfs_ioctl_dev_replace_status_params {
> > #define BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR 0
> > #define BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED 1
> > #define BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED 2
> >+#define BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS 3
> > struct btrfs_ioctl_dev_replace_args {
> > __u64 cmd; /* in */
> > __u64 result; /* out */
> >
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