Re: XFS long delays on disk full

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, Jul 18, 2018 at 02:22:40PM -0700, Andi Kleen wrote:
> Hi,
> 
> I was doing some testing on a 4.18-rc1 kernel, and a single threaded
> test wrote a fairly large file to a XFS file system, causing it to
> fill up.
> 
> After that the process hung in D state for a long time, and only
> recovered after several minutes. Here's the backtrace during
> the hang:
> 
> [<0>] wb_wait_for_completion+0x5e/0x90
> [<0>] sync_inodes_sb+0xc9/0x290

Hmm, these two:

> [<0>] xfs_flush_inodes+0x25/0x30 [xfs]
> [<0>] xfs_file_buffered_aio_write+0x2be/0x300 [xfs]

Offhand I'd guess (while awayish at OSCON) that the fs hit ENOSPC while
trying to write() the file so now we're scanning the fs like mad trying
to free up space preallocations from any open file in the fs.

How big is the fs, how big is the file, how many inodes, how many are
open, which kernel?

--D

> [<0>] __vfs_write+0x114/0x1a0
> [<0>] vfs_write+0xad/0x1a0
> [<0>] ksys_write+0x52/0xc0
> [<0>] do_syscall_64+0x5b/0x160
> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [<0>] 0xffffffffffffffff
> 
> There were no IO errors or similar.
> 
> Expected? Already fixed?
> 
> Thanks,
> -Andi
> 
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