Well, this isn't great timing, since I was going to do 6.15 within the hour.
On Sun, 25 May 2025 at 12:11, Vlastimil Babka <vbabka@xxxxxxx> wrote:
>
> I'm not familiar with this code too much, but I suspect problem was
> introduced by commit fb7d3bc414939 ("mm/filemap: drop streaming/uncached
> pages when writeback completes") and only (more) exposed here.
That bug goes back to 6.13 if so.
But yeah, maybe the drop-behind case never triggers in practice, and I
should just revert commit 974c5e6139db ("xfs: flag as supporting
FOP_DONTCACHE") for now.
That's kind of sad too, but at least that's new to 6.15 and we
wouldn't have a kernel release that triggers this issue.
I realize that Vlastimil had a suggested possible fix, but doing
_that_ kind of surgery at this point in the release isn't an option,
I'm afraid. And delaying 6.15 for this also seems a bit excessive - if
it turns out to be easy to fix, we can always just backport the fix
and undo the revert.
Sounds like a plan?
I'm somewhat surprised that this was only noticed now if it triggers
so easily for Al with xfstests on xfs. But better late than never, I
guess..
Linus
