linux-kernel - Re: [PATCH v5 18/22] docs: add documentation for memfd preservation via LUO

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Message-ID: <CA+CK2bBmSD_YftJ-9w1zidLz2=a4NynnLz_gLPsScF145bu5dQ@mail.gmail.com>
Date: Thu, 13 Nov 2025 11:55:25 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [PATCH v5 18/22] docs: add documentation for memfd preservation
 via LUO

> +Limitations
> +===========
> +
> +The current implementation has the following limitations:
> +
> +Size
> +  Currently the size of the file is limited by the size of the FDT. The FDT can
> +  be at of most ``MAX_PAGE_ORDER`` order. By default this is 4 MiB with 4K
> +  pages. Each page in the file is tracked using 16 bytes. This limits the
> +  maximum size of the file to 1 GiB.

The above should be removed, as we are using KHO vmalloc that resolves
this limitation. Pratyush, I suggest for v6 let's move memfd
documnetation right into the code: memfd_luo.c and
liveupdate/abi/memfd.h, and source it from there.

Keeping documentation with the code helps reduce code/doc divergence.

Pasha