linux-kernel - [PATCH 0/4] convert read_kcore(), vread() to use iterators

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Date:   Sun, 19 Mar 2023 00:20:08 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Baoquan He <bhe@...hat.com>, Uladzislau Rezki <urezki@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH 0/4] convert read_kcore(), vread() to use iterators

While reviewing Baoquan's recent changes to permit vread() access to
vm_map_ram regions of vmalloc allocations, Willy pointed out [1] that it
would be nice to refactor vread() as a whole, since its only user is
read_kcore() and the existing form of vread() necessitates the use of a
bounce buffer.

This patch series does exactly that, as well as adjusting how we read the
kernel text section to avoid the use of a bounce buffer in this case as
well.

This patch series necessarily changes the locking used in vmalloc, however
tests indicate that this has very little impact on allocation performance
(test results are shown in the relevant patch).

This has been tested against the test case which motivated Baoquan's
changes in the first place [2] which continues to function correctly, as
do the vmalloc self tests.

[1] https://lore.kernel.org/all/Y8WfDSRkc%2FOHP3oD@casper.infradead.org/
[2] https://lore.kernel.org/all/87ilk6gos2.fsf@oracle.com/T/#u

Lorenzo Stoakes (4):
  fs/proc/kcore: Avoid bounce buffer for ktext data
  mm: vmalloc: use rwsem, mutex for vmap_area_lock and vmap_block->lock
  fs/proc/kcore: convert read_kcore() to read_kcore_iter()
  mm: vmalloc: convert vread() to vread_iter()

 fs/proc/kcore.c         |  84 +++++++------------
 include/linux/vmalloc.h |   3 +-
 mm/vmalloc.c            | 178 +++++++++++++++++++++-------------------
 3 files changed, 125 insertions(+), 140 deletions(-)

--
2.39.2