From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Steven Price <steven.price@arm.com>
Cc: "Andy Lutomirski" <luto@kernel.org>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Arnd Bergmann" <arnd@arndb.de>, "Borislav Petkov" <bp@alien8.de>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Ingo Molnar" <mingo@redhat.com>,
"James Morse" <james.morse@arm.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Will Deacon" <will@kernel.org>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Mark Rutland" <Mark.Rutland@arm.com>,
"Liang, Kan" <kan.liang@linux.intel.com>,
"Zong Li" <zong.li@sifive.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH v16 11/25] mm: pagewalk: Add p4d_entry() and pgd_entry()
Date: Thu, 12 Dec 2019 12:33:41 +0100 [thread overview]
Message-ID: <7fd20e9f-822a-897d-218e-bddf135fd33d@shipmail.org> (raw)
In-Reply-To: <13280f9e-6f03-e1fd-659a-31462ba185b0@shipmail.org>
On 12/12/19 12:23 PM, Thomas Hellström (VMware) wrote:
> On 12/6/19 2:53 PM, Steven Price wrote:
>> pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
>> ("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
>> no users. We're about to add users so reintroduce them, along with
>> p4d_entry() as we now have 5 levels of tables.
>>
>> Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
>> PUD-sized transparent hugepages") already re-added pud_entry() but with
>> different semantics to the other callbacks. Since there have never
>> been upstream users of this, revert the semantics back to match the
>> other callbacks. This means pud_entry() is called for all entries, not
>> just transparent huge pages.
>
> Actually, there are two users of pud_entry(), in hmm.c and since
> 5.5rc1 also mapping_dirty_helpers.c. The latter one is unproblematic
> and requires no attention but the one in hmm.c is probably largely
> untested, and seems to assume it was called outside of the spinlock.
>
> The problem with the current patch is that the hmm pud_entry will
> traverse also pmds, so that will be done twice now.
>
> In another thread we were discussing a means of rerunning the level
> (in case of a race), or continuing after a level, based on the return
> value after the callback. The change was fairly invasive,
>
Hmm. Forgot to remove the above text that appears twice. :(. The correct
one is inline below.
>
>> Tested-by: Zong Li <zong.li@sifive.com>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> include/linux/pagewalk.h | 19 +++++++++++++------
>> mm/pagewalk.c | 27 ++++++++++++++++-----------
>> 2 files changed, 29 insertions(+), 17 deletions(-)
>>
>> diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
>> index 6ec82e92c87f..06790f23957f 100644
>> --- a/include/linux/pagewalk.h
>> +++ b/include/linux/pagewalk.h
>> @@ -8,15 +8,15 @@ struct mm_walk;
>> /**
>> * mm_walk_ops - callbacks for walk_page_range
>> - * @pud_entry: if set, called for each non-empty PUD
>> (2nd-level) entry
>> - * this handler should only handle pud_trans_huge() puds.
>> - * the pmd_entry or pte_entry callbacks will be used for
>> - * regular PUDs.
>> - * @pmd_entry: if set, called for each non-empty PMD
>> (3rd-level) entry
>> + * @pgd_entry: if set, called for each non-empty PGD
>> (top-level) entry
>> + * @p4d_entry: if set, called for each non-empty P4D entry
>> + * @pud_entry: if set, called for each non-empty PUD entry
>> + * @pmd_entry: if set, called for each non-empty PMD entry
>> * this handler is required to be able to handle
>> * pmd_trans_huge() pmds. They may simply choose to
>> * split_huge_page() instead of handling it explicitly.
>> - * @pte_entry: if set, called for each non-empty PTE
>> (4th-level) entry
>> + * @pte_entry: if set, called for each non-empty PTE
>> (lowest-level)
>> + * entry
>> * @pte_hole: if set, called for each hole at all levels
>> * @hugetlb_entry: if set, called for each hugetlb entry
>> * @test_walk: caller specific callback function to
>> determine whether
>> @@ -27,8 +27,15 @@ struct mm_walk;
>> * @pre_vma: if set, called before starting walk on a
>> non-null vma.
>> * @post_vma: if set, called after a walk on a non-null
>> vma, provided
>> * that @pre_vma and the vma walk succeeded.
>> + *
>> + * p?d_entry callbacks are called even if those levels are folded on a
>> + * particular architecture/configuration.
>> */
>> struct mm_walk_ops {
>> + int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
>> + unsigned long next, struct mm_walk *walk);
>> + int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
>> + unsigned long next, struct mm_walk *walk);
>> int (*pud_entry)(pud_t *pud, unsigned long addr,
>> unsigned long next, struct mm_walk *walk);
>> int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
>> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
>> index ea0b9e606ad1..c089786e7a7f 100644
>> --- a/mm/pagewalk.c
>> +++ b/mm/pagewalk.c
>> @@ -94,15 +94,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned
>> long addr, unsigned long end,
>> }
>> if (ops->pud_entry) {
>> - spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
>> -
>> - if (ptl) {
>> - err = ops->pud_entry(pud, addr, next, walk);
>> - spin_unlock(ptl);
>> - if (err)
>> - break;
>> - continue;
>> - }
>> + err = ops->pud_entry(pud, addr, next, walk);
>> + if (err)
>> + break;
>
> Actually, there are two current users of pud_entry(), in hmm.c and
> since 5.5rc1 also mapping_dirty_helpers.c. The latter one is
> unproblematic and requires no attention but the one in hmm.c is
> probably largely untested, and seems to assume it was called outside
> of the spinlock.
>
> The problem with the current patch is that the hmm pud_entry will
> traverse also pmds, so that will now be done twice.
>
> /Thomas
>
next prev parent reply other threads:[~2019-12-12 11:33 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-06 13:52 [PATCH v16 00/25] Generic page walk and ptdump Steven Price
2019-12-06 13:52 ` [PATCH v16 01/25] mm: Add generic p?d_leaf() macros Steven Price
2019-12-06 13:52 ` [PATCH v16 02/25] arc: mm: Add p?d_leaf() definitions Steven Price
2019-12-06 13:52 ` [PATCH v16 03/25] arm: " Steven Price
2019-12-06 13:52 ` [PATCH v16 04/25] arm64: " Steven Price
2019-12-06 13:52 ` [PATCH v16 05/25] mips: " Steven Price
2019-12-06 13:52 ` [PATCH v16 06/25] powerpc: " Steven Price
2019-12-09 11:08 ` Michael Ellerman
2019-12-09 13:06 ` Steven Price
2019-12-06 13:52 ` [PATCH v16 07/25] riscv: " Steven Price
2019-12-06 13:52 ` [PATCH v16 08/25] s390: " Steven Price
2019-12-06 13:53 ` [PATCH v16 09/25] sparc: " Steven Price
2019-12-06 13:53 ` [PATCH v16 10/25] x86: " Steven Price
2019-12-06 13:53 ` [PATCH v16 11/25] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-12-12 11:23 ` Thomas Hellström (VMware)
2019-12-12 11:33 ` Thomas Hellström (VMware) [this message]
2019-12-12 13:15 ` Steven Price
2019-12-12 14:04 ` Thomas Hellström (VMware)
2019-12-12 15:18 ` Steven Price
2019-12-06 13:53 ` [PATCH v16 12/25] mm: pagewalk: Allow walking without vma Steven Price
2019-12-06 13:53 ` [PATCH v16 13/25] mm: pagewalk: Don't lock PTEs for walk_page_range_novma() Steven Price
2019-12-10 11:23 ` kbuild test robot
2019-12-11 15:54 ` Steven Price
2019-12-11 17:12 ` Luc Van Oostenryck
2019-12-11 17:19 ` Qian Cai
2019-12-06 13:53 ` [PATCH v16 14/25] mm: pagewalk: fix termination condition in walk_pte_range() Steven Price
2019-12-06 13:53 ` [PATCH v16 15/25] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-12-06 13:53 ` [PATCH v16 16/25] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
2019-12-06 13:53 ` [PATCH v16 17/25] x86: mm: Point to struct seq_file from struct pg_state Steven Price
2019-12-06 13:53 ` [PATCH v16 18/25] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-12-06 13:53 ` [PATCH v16 19/25] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-12-06 13:53 ` [PATCH v16 20/25] x86: mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-12-06 13:53 ` [PATCH v16 21/25] mm: Add generic ptdump Steven Price
2019-12-06 13:53 ` [PATCH v16 22/25] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
2019-12-06 13:53 ` [PATCH v16 23/25] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-12-06 13:53 ` [PATCH v16 24/25] arm64: mm: Display non-present entries in ptdump Steven Price
2019-12-06 13:53 ` [PATCH v16 25/25] mm: ptdump: Reduce level numbers by 1 in note_page() Steven Price
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7fd20e9f-822a-897d-218e-bddf135fd33d@shipmail.org \
--to=thomas_os@shipmail.org \
--cc=Mark.Rutland@arm.com \
--cc=akpm@linux-foundation.org \
--cc=ard.biesheuvel@linaro.org \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=james.morse@arm.com \
--cc=jglisse@redhat.com \
--cc=kan.liang@linux.intel.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=steven.price@arm.com \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=zong.li@sifive.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).