linux-kernel - Re: [PATCH v2 05/13] mm: add basic VMA flag operation helper functions

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Message-ID: <vrbggto75ugvpa5wtugmayr7yops6cnvygit42f2md646y6qnx@3vzc7taleijw>
Date: Fri, 6 Feb 2026 17:35:49 +0000
From: Pedro Falcato <pfalcato@...e.de>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
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Subject: Re: [PATCH v2 05/13] mm: add basic VMA flag operation helper
 functions

On Thu, Jan 22, 2026 at 04:06:14PM +0000, Lorenzo Stoakes wrote:
> Now we have the mk_vma_flags() macro helper which permits easy
> specification of any number of VMA flags, add helper functions which
> operate with vma_flags_t parameters.
> 
> This patch provides vma_flags_test[_mask](), vma_flags_set[_mask]() and
> vma_flags_clear[_mask]() respectively testing, setting and clearing flags
> with the _mask variants accepting vma_flag_t parameters, and the non-mask
> variants implemented as macros which accept a list of flags.
> 
> This allows us to trivially test/set/clear aggregate VMA flag values as
> necessary, for instance:
> 
> 	if (vma_flags_test(&flags, VMA_READ_BIT, VMA_WRITE_BIT))
> 		goto readwrite;

I'm not a huge fan of the _test ambiguity here, but more words makes it uglier :/
I think I can live with it though.

> 
> 	vma_flags_set(&flags, VMA_READ_BIT, VMA_WRITE_BIT);
> 
> 	vma_flags_clear(&flags, VMA_READ_BIT, VMA_WRITE_BIT);
> 

The variadic-ness here is very nice though.

> We also add a function for testing that ALL flags are set for convenience,
> e.g.:
> 
> 	if (vma_flags_test_all(&flags, VMA_READ_BIT, VMA_MAYREAD_BIT)) {
> 		/* Both READ and MAYREAD flags set */
> 		...
> 	}
> 
> The compiler generates optimal assembly for each such that they behave as
> if the caller were setting the bitmap flags manually.
> 
> This is important for e.g. drivers which manipulate flag values rather than
> a VMA's specific flag values.
> 
> We also add helpers for testing, setting and clearing flags for VMA's and
> VMA descriptors to reduce boilerplate.
> 
> Also add the EMPTY_VMA_FLAGS define to aid initialisation of empty flags.
> 
> Finally, update the userland VMA tests to add the helpers there so they can
> be utilised as part of userland testing.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Pedro Falcato <pfalcato@...e.de> 

-- 
Pedro