From: Matthew Wilcox <willy@infradead.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com,
wangkefeng.wang@huawei.com, 21cnbao@gmail.com,
ryan.roberts@arm.com, ioworker0@gmail.com, da.gomez@samsung.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 1/2] mm: shmem: add large folio support to the write and fallocate paths
Date: Thu, 26 Sep 2024 13:16:33 +0100 [thread overview]
Message-ID: <ZvVQoY8Tn_BNc79T@casper.infradead.org> (raw)
In-Reply-To: <c03ec1cb1392332726ab265a3d826fe1c408c7e7.1727338549.git.baolin.wang@linux.alibaba.com>
On Thu, Sep 26, 2024 at 04:27:26PM +0800, Baolin Wang wrote:
> +static inline unsigned int
> +shmem_mapping_size_order(struct address_space *mapping, pgoff_t index, size_t size)
> +{
> + unsigned int order = get_order(max_t(size_t, size, PAGE_SIZE));
Why introduce the max_t() call here? Did nobody read the documentation
or implementation for get_order() before writing this patch?
Besides, get_order() is wrong (at least relative to other filesystems).
get_order() rounds up instead of down, so what should we do for a write()
of size 512 * 1024 + 1 byte? Other filesystems allocate an order-8 folio
plus an order-0 folio. This code would have us allocate an order-9 folio.
I think that's a bad idea.
next prev parent reply other threads:[~2024-09-26 12:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-26 8:27 [RFC PATCH v2 0/2] Support large folios for tmpfs Baolin Wang
2024-09-26 8:27 ` [RFC PATCH v2 1/2] mm: shmem: add large folio support to the write and fallocate paths Baolin Wang
2024-09-26 12:16 ` Matthew Wilcox [this message]
2024-09-26 12:58 ` Daniel Gomez
2024-09-26 13:40 ` Matthew Wilcox
2024-09-27 2:12 ` Baolin Wang
2024-09-26 8:27 ` [RFC PATCH v2 2/2] mm: shmem: use mTHP interface to control huge orders for tmpfs Baolin Wang
2024-09-26 12:20 ` [RFC PATCH v2 0/2] Support large folios " Matthew Wilcox
2024-09-27 2:36 ` Baolin Wang
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