Re: buffer cache simplification v4

[Brian Foster <bfoster@redhat.com>]

On Mon, Mar 16, 2026 at 04:41:32PM +0100, Christoph Hellwig wrote:
> Hi all,
> 
> this series has a few old patches that simplify the LRU handling, and
> moves back to only having a per-buftarg hash now that the buffer hash
> is using the scalable rhashtable.  While some of this looks like
> performance work, performance and scalability is unchanged even on the
> 80 core dual socket system I test this on.  Besides cleaning up the
> code nice, it also happens to fix a syzcaller reported use after free
> during buffer shutdown, which happened incidentally because of how the
> tear down of the buftarg vs the perag structures is handled.
> 
> Changes since v3:
>  - split the change to handling how referenced buffers on the LRU
>    are handled into a separate patch
> 

It looks like there's a patch ordering problem or something here. It
doesn't apply to master, and looks like patch 1 is trying to modify
hunks that don't yet exist. A local rebase issue related to reordering
the change in patch 3 perhaps..?

Brian

> Changes since v2:
>  - mark b_hold as signed in patch 1 before removing it in patch 2
>  - document the changed locking in xfs_buf_rele_cached.
> 
> Changes since v2:
>  - add more details and a link to a commit message
> 
> Diffstat:
>  libxfs/xfs_ag.c |   13 ----
>  libxfs/xfs_ag.h |    2 
>  xfs_buf.c       |  148 ++++++++++++++++++++------------------------------------
>  xfs_buf.h       |   14 +----
>  xfs_buf_mem.c   |   11 ----
>  xfs_trace.h     |   10 +--
>  6 files changed, 66 insertions(+), 132 deletions(-)
>