linux-kernel - [PATCH next 0/3] iov: Optimise user copies

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Message-Id: <20250321224557.3847-1-david.laight.linux@gmail.com>
Date: Fri, 21 Mar 2025 22:45:54 +0000
From: David Laight <david.laight.linux@...il.com>
To: linux-kernel@...r.kernel.org
Cc: David Laight <david.laight.linux@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	David Howells <dhowells@...hat.com>,
	Matthew Wilcox <willy@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH next 0/3] iov: Optimise user copies

The speculation barrier in access_ok() is expensive.

The first patch removes the initial checks when reading the iovec[].
The checks are repeated before the actual copy.

The second patch uses 'user address masking' if supported.

The third removes a lot of code for single entry iovec[].

David Laight (3):
  Remove access_ok() from import_iovec()
  Use masked user accesses
  Optimise __import_iovec_ubuf()

 lib/iov_iter.c | 97 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 63 insertions(+), 34 deletions(-)

-- 
2.39.5