From: Peter Xu <peterx@redhat.com>
To: Axel Rasmussen <axelrasmussen@google.com>
Cc: "Alexander Viro" <viro@zeniv.linux.org.uk>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Chinwen Chang" <chinwen.chang@mediatek.com>,
"Huang Ying" <ying.huang@intel.com>,
"Ingo Molnar" <mingo@redhat.com>, "Jann Horn" <jannh@google.com>,
"Jerome Glisse" <jglisse@redhat.com>,
"Lokesh Gidra" <lokeshgidra@google.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Koutný" <mkoutny@suse.com>,
"Michel Lespinasse" <walken@google.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Mike Rapoport" <rppt@linux.vnet.ibm.com>,
"Nicholas Piggin" <npiggin@gmail.com>, "Shaohua Li" <shli@fb.com>,
"Shawn Anastasio" <shawn@anastas.io>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Steven Price" <steven.price@arm.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, "Adam Ruprecht" <ruprecht@google.com>,
"Cannon Matthews" <cannonmatthews@google.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
"David Rientjes" <rientjes@google.com>,
"Oliver Upton" <oupton@google.com>
Subject: Re: [PATCH 5/9] userfaultfd: add minor fault registration mode
Date: Thu, 21 Jan 2021 13:49:38 -0500 [thread overview]
Message-ID: <20210121184938.GD260413@xz-x1> (raw)
In-Reply-To: <20210115190451.3135416-6-axelrasmussen@google.com>
Hi, Axel,
On Fri, Jan 15, 2021 at 11:04:47AM -0800, Axel Rasmussen wrote:
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index c63ccdae3eab..7aa1461e1a8b 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -71,6 +71,11 @@ static inline bool userfaultfd_wp(struct vm_area_struct *vma)
> return vma->vm_flags & VM_UFFD_WP;
> }
>
> +static inline bool userfaultfd_minor(struct vm_area_struct *vma)
> +{
> + return vma->vm_flags & VM_UFFD_MINOR;
> +}
> +
> static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
> pte_t pte)
> {
> @@ -85,7 +90,7 @@ static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
>
> static inline bool userfaultfd_armed(struct vm_area_struct *vma)
> {
> - return vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP);
> + return vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR);
> }
Maybe move the __VM_UFFD_FLAGS into this header so use it too here?
[...]
> diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
> index 5f2d88212f7c..1cc2cd8a5279 100644
> --- a/include/uapi/linux/userfaultfd.h
> +++ b/include/uapi/linux/userfaultfd.h
> @@ -19,15 +19,19 @@
> * means the userland is reading).
> */
> #define UFFD_API ((__u64)0xAA)
> +#define UFFD_API_REGISTER_MODES (UFFDIO_REGISTER_MODE_MISSING | \
> + UFFDIO_REGISTER_MODE_WP | \
> + UFFDIO_REGISTER_MODE_MINOR)
> #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \
> UFFD_FEATURE_EVENT_FORK | \
> UFFD_FEATURE_EVENT_REMAP | \
> - UFFD_FEATURE_EVENT_REMOVE | \
> + UFFD_FEATURE_EVENT_REMOVE | \
> UFFD_FEATURE_EVENT_UNMAP | \
> UFFD_FEATURE_MISSING_HUGETLBFS | \
> UFFD_FEATURE_MISSING_SHMEM | \
> UFFD_FEATURE_SIGBUS | \
> - UFFD_FEATURE_THREAD_ID)
> + UFFD_FEATURE_THREAD_ID | \
> + UFFD_FEATURE_MINOR_FAULT_HUGETLBFS)
I'd remove the "_FAULT" to align with the missing features...
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 61d6346ed009..2b3741d6130c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4377,6 +4377,37 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
> }
> }
>
> + /* Check for page in userfault range. */
> + if (!new_page && userfaultfd_minor(vma)) {
> + u32 hash;
> + struct vm_fault vmf = {
> + .vma = vma,
> + .address = haddr,
> + .flags = flags,
> + /*
> + * Hard to debug if it ends up being used by a callee
> + * that assumes something about the other uninitialized
> + * fields... same as in memory.c
> + */
> + };
> +
> + unlock_page(page);
> +
> + /*
> + * hugetlb_fault_mutex and i_mmap_rwsem must be dropped before
> + * handling userfault. Reacquire after handling fault to make
> + * calling code simpler.
> + */
> +
> + hash = hugetlb_fault_mutex_hash(mapping, idx);
> + mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> + i_mmap_unlock_read(mapping);
> + ret = handle_userfault(&vmf, VM_UFFD_MINOR);
> + i_mmap_lock_read(mapping);
> + mutex_lock(&hugetlb_fault_mutex_table[hash]);
> + goto out;
I figured it easier if the whole chunk be put into the else block right after
find_lock_page(); will that work the same?
It's just not obviously clear on when we'll go into this block otherwise,
basically the dependency of new_page variable and when it's unset.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2021-01-21 19:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 19:04 [PATCH 0/9] userfaultfd: add minor fault handling Axel Rasmussen
2021-01-15 19:04 ` [PATCH 1/9] hugetlb: Pass vma into huge_pte_alloc() Axel Rasmussen
2021-01-15 19:04 ` [PATCH 2/9] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Axel Rasmussen
2021-01-21 18:52 ` Peter Xu
2021-01-15 19:04 ` [PATCH 3/9] mm/hugetlb: Move flush_hugetlb_tlb_range() into hugetlb.h Axel Rasmussen
2021-01-15 19:04 ` [PATCH 4/9] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp Axel Rasmussen
2021-01-15 19:04 ` [PATCH 5/9] userfaultfd: add minor fault registration mode Axel Rasmussen
2021-01-21 18:49 ` Peter Xu [this message]
2021-01-15 19:04 ` [PATCH 6/9] userfaultfd: disable huge PMD sharing for MINOR registered VMAs Axel Rasmussen
2021-01-21 18:59 ` Peter Xu
2021-01-15 19:04 ` [PATCH 7/9] userfaultfd: add UFFDIO_CONTINUE ioctl Axel Rasmussen
2021-01-21 22:46 ` Peter Xu
2021-01-21 23:46 ` Axel Rasmussen
2021-01-15 19:04 ` [PATCH 8/9] userfaultfd: update documentation to describe minor fault handling Axel Rasmussen
2021-01-15 19:04 ` [PATCH 9/9] userfaultfd/selftests: add test exercising " Axel Rasmussen
2021-01-21 19:12 ` [PATCH 0/9] userfaultfd: add " Peter Xu
2021-01-21 22:13 ` Axel Rasmussen
2021-01-21 22:37 ` Peter Xu
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=20210121184938.GD260413@xz-x1 \
--to=peterx@redhat.com \
--cc=aarcange@redhat.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=axelrasmussen@google.com \
--cc=cannonmatthews@google.com \
--cc=catalin.marinas@arm.com \
--cc=chinwen.chang@mediatek.com \
--cc=dgilbert@redhat.com \
--cc=jannh@google.com \
--cc=jglisse@redhat.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lokeshgidra@google.com \
--cc=mike.kravetz@oracle.com \
--cc=mingo@redhat.com \
--cc=mkoutny@suse.com \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=oupton@google.com \
--cc=rientjes@google.com \
--cc=rostedt@goodmis.org \
--cc=rppt@linux.vnet.ibm.com \
--cc=ruprecht@google.com \
--cc=shawn@anastas.io \
--cc=shli@fb.com \
--cc=steven.price@arm.com \
--cc=vbabka@suse.cz \
--cc=viro@zeniv.linux.org.uk \
--cc=walken@google.com \
--cc=willy@infradead.org \
--cc=ying.huang@intel.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).