Re: btrfs-rmw-2: page allocation failure: order:1, mode:0x8020

[Marc MERLIN <marc@merlins.org>]

On Thu, Mar 20, 2014 at 12:13:36AM +0000, Chris Mason wrote:
> >Should I double it?
> >
> >For now, I have the copy running again, and it's been going for 8 hours
> >without failure on the old kernel but of course that doesn't mean my 2TB
> >copy will complete without hitting the bug again.
> 
> Sorry, I misspoke, you should bump /proc/sys/vm/min_free_kbytes.  Honestly
> though, it¹s just a bug in the mvs driver.  Atomic 8K allocations are
> doomed to fail eventually.

Gotcha
polgara:/mnt/btrfs_backupcopy# cat /proc/sys/vm/min_free_kbytes
45056
polgara:/mnt/btrfs_backupcopy# echo 100000 > /proc/sys/vm/min_free_kbytes
polgara:/mnt/btrfs_backupcopy# cat /proc/sys/vm/min_free_kbytes
100000
polgara:/mnt/btrfs_backupcopy# 
 
> The driver should either busy loop until the allocation completes (really
> not a great choice), gracefully deal with the failure (looks tricky), or
> preallocate the space (like the rest of the block layer).

Gotcha. I'll report this to the folks maintaining the marvel driver.

So just to make sure I got you right, although the page allocation failure
was shown in btrfs, it's really the underlying marvel driver at fault here,
and there isn't really anything to change on the btrfs side, correct?

Thanks,
Marc
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Microsoft is to operating systems ....
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