linux-kernel - Re: [PATCH v5 03/22] cachefiles: introduce on-demand read mode

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Message-ID: <1029982.1647872043@warthog.procyon.org.uk>
Date:   Mon, 21 Mar 2022 14:14:03 +0000
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, Jeffle Xu <jefflexu@...ux.alibaba.com>,
        linux-cachefs@...hat.com, xiang@...nel.org, chao@...nel.org,
        linux-erofs@...ts.ozlabs.org, torvalds@...ux-foundation.org,
        gregkh@...uxfoundation.org, linux-fsdevel@...r.kernel.org,
        joseph.qi@...ux.alibaba.com, bo.liu@...ux.alibaba.com,
        tao.peng@...ux.alibaba.com, gerry@...ux.alibaba.com,
        eguan@...ux.alibaba.com, linux-kernel@...r.kernel.org,
        luodaowen.backend@...edance.com
Subject: Re: [PATCH v5 03/22] cachefiles: introduce on-demand read mode

Matthew Wilcox <willy@...radead.org> wrote:

> Why do you have a separate rwlock when the xarray already has its own
> spinlock?  This is usually a really bad idea.

Jeffle wants to hold a lock across the CACHEFILES_DEAD check and the xarray
access.

However, he tells xarray to do a GFP_KERNEL alloc whilst holding the rwlock:-/

David