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Wed, 22 Mar 2023 11:57:06 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro , Lorenzo Stoakes Subject: [PATCH v7 0/4] convert read_kcore(), vread() to use iterators Date: Wed, 22 Mar 2023 18:57:00 +0000 Message-Id: X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: r1fzgedz7jjnmp4cicimso43x67nwe4e X-Rspam-User: X-Rspamd-Queue-Id: C3ACC16000D X-Rspamd-Server: rspam06 X-HE-Tag: 1679511429-702615 X-HE-Meta: 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 w83HQ1mj 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 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 v7: - Keep trying to fault in memory until the vmalloc read operation completes. v6: - Correct copy_page_to_iter_nofault() to handle -EFAULT case correctly. https://lore.kernel.org/all/cover.1679496827.git.lstoakes@gmail.com/ v5: - Do not rename fpos to ppos in read_kcore_iter() to avoid churn. - Fix incorrect commit messages after prior revisions altered the approach. - Replace copy_page_to_iter_atomic() with copy_page_to_iter_nofault() and adjust it to be able to handle compound pages. This uses copy_to_user_nofault() which ensures page faults are disabled during copy which kmap_local_page() was not doing. - Only try to fault in pages if we are unable to copy in the first place and try only once to avoid any risk of spinning. - Do not zero memory in aligned_vread_iter() if we couldn't copy it. - Fix mistake in zeroing missing or unpopulated blocks in vmap_ram_vread_iter(). https://lore.kernel.org/linux-mm/cover.1679494218.git.lstoakes@gmail.com/ v4: - Fixup mistake in email client which orphaned patch emails from the cover letter. https://lore.kernel.org/all/cover.1679431886.git.lstoakes@gmail.com v3: - Revert introduction of mutex/rwsem in vmalloc - Introduce copy_page_to_iter_atomic() iovec function - Update vread_iter() and descendent functions to use only this - Fault in user pages before calling vread_iter() - Use const char* in vread_iter() and descendent functions - Updated commit messages based on feedback - Extend vread functions to always check how many bytes we could copy. If at any stage we are unable to copy/zero, abort and return the number of bytes we did copy. https://lore.kernel.org/all/cover.1679354384.git.lstoakes@gmail.com/ v2: - Fix ordering of vread_iter() parameters - Fix nommu vread() -> vread_iter() https://lore.kernel.org/all/cover.1679209395.git.lstoakes@gmail.com/ v1: https://lore.kernel.org/all/cover.1679183626.git.lstoakes@gmail.com/ Lorenzo Stoakes (4): fs/proc/kcore: avoid bounce buffer for ktext data fs/proc/kcore: convert read_kcore() to read_kcore_iter() iov_iter: add copy_page_to_iter_nofault() mm: vmalloc: convert vread() to vread_iter() fs/proc/kcore.c | 85 +++++++-------- include/linux/uio.h | 2 + include/linux/vmalloc.h | 3 +- lib/iov_iter.c | 48 +++++++++ mm/nommu.c | 10 +- mm/vmalloc.c | 234 +++++++++++++++++++++++++--------------- 6 files changed, 243 insertions(+), 139 deletions(-) -- 2.39.2