Re: [PATCH 0/2] Btrfs: fixes for an ENOSPC issue that left a fs unusable

[Chris Mason <clm@fb.com>]

On Fri, Nov 13, 2015 at 03:20:30PM +0000, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The following pair of changes fix an issue observed in a production
> environment where any file operations done by a package manager failed
> with ENOSPC. Forcing a commit of the current transaction (through "sync")
> didn't help, a balance operation with the filters -dusage=0 didn't help
> either and the issue persisted even after rebooting the machine. There
> were many data blocks groups that were unused, but they weren't getting
> deleted by the cleaner kthread because whenever it tried to start a
> transaction to delete a block group it got -ENOSPC error, which it silently
> ignores (as it does for any other error).
> 
> So these just make sure we fallback to use the global reserve, if -ENOSPC
> is encountered through the standard allocation path, to delete block groups
> as we do already for inode unlink operations. Another issue fixed is hitting
> a BUG_ON() when removing a block group due to -ENSPC failure when creating
> the orphan item for its free space cache inode. This second issue has
> been reported by a few users in the mailing list and bugzilla (for example
> at http://www.spinics.net/lists/linux-btrfs/msg46070.html).
> 
> These changes are also available at:
> http://git.kernel.org/cgit/linux/kernel/git/fdmanana/linux.git/log/?h=integration-4.4

I like both of these.  I'll queue for after rc1.

-chris