lkml.org 
[lkml]   [2020]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] overlayfs: Report writeback errors on upper
On Mon, Dec 28, 2020 at 08:25:50AM -0500, Jeff Layton wrote:
> To be clear, the main thing you'll lose with the method above is the
> ability to see an unseen error on a newly opened fd, if there was an
> overlayfs mount using the same upper sb before your open occurred.
>
> IOW, consider two overlayfs mounts using the same upper layer sb:
>
> ovlfs1 ovlfs2
> ----------------------------------------------------------------------
> mount
> open fd1
> write to fd1
> <writeback fails>
> mount (upper errseq_t SEEN flag marked)
> open fd2
> syncfs(fd2)
> syncfs(fd1)
>
>
> On a "normal" (non-overlay) fs, you'd get an error back on both syncfs
> calls. The first one has a sample from before the error occurred, and
> the second one has a sample of 0, due to the fact that the error was
> unseen at open time.
>
> On overlayfs, with the intervening mount of ovlfs2, syncfs(fd1) will
> return an error and syncfs(fd2) will not. If we split the SEEN flag into
> two, then we can ensure that they both still get an error in this
> situation.

But do we need to? If the inode has been evicted we also lose the errno.
The guarantee we provide is that a fd that was open before the error
occurred will see the error. An fd that's opened after the error occurred
may or may not see the error.

\
 
 \ /
  Last update: 2020-12-28 16:58    [W:0.209 / U:0.992 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site