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Date: Fri, 13 Jul 2018 06:49:16 +0000
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To: Dan Williams <dan.j.williams@...el.com>
CC: "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
"hch@....de" <hch@....de>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jack@...e.cz" <jack@...e.cz>,
"ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH v5 06/11] mm, memory_failure: Collect mapping size in
collect_procs()
On Wed, Jul 04, 2018 at 02:40:55PM -0700, Dan Williams wrote:
> In preparation for supporting memory_failure() for dax mappings, teach
> collect_procs() to also determine the mapping size. Unlike typical
> mappings the dax mapping size is determined by walking page-table
> entries rather than using the compound-page accounting for THP pages.
>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Looks good to me.
Acked-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> ---
> mm/memory-failure.c | 81 +++++++++++++++++++++++++--------------------------
> 1 file changed, 40 insertions(+), 41 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 9d142b9b86dc..4d70753af59c 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -174,22 +174,51 @@ int hwpoison_filter(struct page *p)
> EXPORT_SYMBOL_GPL(hwpoison_filter);
>
> /*
> + * Kill all processes that have a poisoned page mapped and then isolate
> + * the page.
> + *
> + * General strategy:
> + * Find all processes having the page mapped and kill them.
> + * But we keep a page reference around so that the page is not
> + * actually freed yet.
> + * Then stash the page away
> + *
> + * There's no convenient way to get back to mapped processes
> + * from the VMAs. So do a brute-force search over all
> + * running processes.
> + *
> + * Remember that machine checks are not common (or rather
> + * if they are common you have other problems), so this shouldn't
> + * be a performance issue.
> + *
> + * Also there are some races possible while we get from the
> + * error detection to actually handle it.
> + */
> +
> +struct to_kill {
> + struct list_head nd;
> + struct task_struct *tsk;
> + unsigned long addr;
> + short size_shift;
> + char addr_valid;
> +};
> +
> +/*
> * Send all the processes who have the page mapped a signal.
> * ``action optional'' if they are not immediately affected by the error
> * ``action required'' if error happened in current execution context
> */
> -static int kill_proc(struct task_struct *t, unsigned long addr,
> - unsigned long pfn, struct page *page, int flags)
> +static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
> {
> - short addr_lsb;
> + struct task_struct *t = tk->tsk;
> + short addr_lsb = tk->size_shift;
> int ret;
>
> pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
> pfn, t->comm, t->pid);
> - addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
>
> if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
> - ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)addr,
> + ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr,
> addr_lsb, current);
> } else {
> /*
> @@ -198,7 +227,7 @@ static int kill_proc(struct task_struct *t, unsigned long addr,
> * This could cause a loop when the user sets SIGBUS
> * to SIG_IGN, but hopefully no one will do that?
> */
> - ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)addr,
> + ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
> addr_lsb, t); /* synchronous? */
> }
> if (ret < 0)
> @@ -235,35 +264,6 @@ void shake_page(struct page *p, int access)
> EXPORT_SYMBOL_GPL(shake_page);
>
> /*
> - * Kill all processes that have a poisoned page mapped and then isolate
> - * the page.
> - *
> - * General strategy:
> - * Find all processes having the page mapped and kill them.
> - * But we keep a page reference around so that the page is not
> - * actually freed yet.
> - * Then stash the page away
> - *
> - * There's no convenient way to get back to mapped processes
> - * from the VMAs. So do a brute-force search over all
> - * running processes.
> - *
> - * Remember that machine checks are not common (or rather
> - * if they are common you have other problems), so this shouldn't
> - * be a performance issue.
> - *
> - * Also there are some races possible while we get from the
> - * error detection to actually handle it.
> - */
> -
> -struct to_kill {
> - struct list_head nd;
> - struct task_struct *tsk;
> - unsigned long addr;
> - char addr_valid;
> -};
> -
> -/*
> * Failure handling: if we can't find or can't kill a process there's
> * not much we can do. We just print a message and ignore otherwise.
> */
> @@ -292,6 +292,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
> }
> tk->addr = page_address_in_vma(p, vma);
> tk->addr_valid = 1;
> + tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
>
> /*
> * In theory we don't have to kill when the page was
> @@ -317,9 +318,8 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
> * Also when FAIL is set do a force kill because something went
> * wrong earlier.
> */
> -static void kill_procs(struct list_head *to_kill, int forcekill,
> - bool fail, struct page *page, unsigned long pfn,
> - int flags)
> +static void kill_procs(struct list_head *to_kill, int forcekill, bool fail,
> + unsigned long pfn, int flags)
> {
> struct to_kill *tk, *next;
>
> @@ -342,8 +342,7 @@ static void kill_procs(struct list_head *to_kill, int forcekill,
> * check for that, but we need to tell the
> * process anyways.
> */
> - else if (kill_proc(tk->tsk, tk->addr,
> - pfn, page, flags) < 0)
> + else if (kill_proc(tk, pfn, flags) < 0)
> pr_err("Memory failure: %#lx: Cannot send advisory machine check signal to %s:%d\n",
> pfn, tk->tsk->comm, tk->tsk->pid);
> }
> @@ -1012,7 +1011,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
> * any accesses to the poisoned memory.
> */
> forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
> - kill_procs(&tokill, forcekill, !unmap_success, p, pfn, flags);
> + kill_procs(&tokill, forcekill, !unmap_success, pfn, flags);
>
> return unmap_success;
> }
>
>
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