From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: Andrei Vagin <avagin@gmail.com>
Cc: linux-mm@kvack.org, "Andrew Morton" <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, "Oleg Nesterov" <oleg@redhat.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Michal Hocko" <mhocko@kernel.org>,
"Cyrill Gorcunov" <gorcunov@gmail.com>,
"Kirill Tkhai" <ktkhai@virtuozzo.com>,
"Michal Koutný" <mkoutny@suse.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Roman Gushchin" <guro@fb.com>,
"Dmitry Safonov" <dima@arista.com>
Subject: Re: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files
Date: Thu, 13 Jun 2019 11:15:50 +0300 [thread overview]
Message-ID: <f15478b5-098f-e1be-0928-62f46cff77e7@yandex-team.ru> (raw)
In-Reply-To: <20190612231426.GA3639@gmail.com>
On 13.06.2019 2:14, Andrei Vagin wrote:
> On Sun, Jun 09, 2019 at 01:09:00PM +0300, Konstantin Khlebnikov wrote:
>> Do not stuck forever if something wrong.
>> Killable lock allows to cleanup stuck tasks and simplifies investigation.
>
> This patch breaks the CRIU project, because stat() returns EINTR instead
> of ENOENT:
>
> [root@fc24 criu]# stat /proc/self/map_files/0-0
> stat: cannot stat '/proc/self/map_files/0-0': Interrupted system call
Good catch.
It seems CRIU tests has good coverage for darkest corners of kernel API.
Kernel CI projects should use it. I suppose you know how to promote this. =)
>
> Here is one inline comment with the fix for this issue.
>
>>
>> It seems ->d_revalidate() could return any error (except ECHILD) to
>> abort validation and pass error as result of lookup sequence.
>>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>> Reviewed-by: Roman Gushchin <guro@fb.com>
>> Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
>> Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>
> It was nice to see all four of you in one place :).
>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> ---
>> fs/proc/base.c | 27 +++++++++++++++++++++------
>> 1 file changed, 21 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 9c8ca6cd3ce4..515ab29c2adf 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -1962,9 +1962,12 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
>> goto out;
>>
>> if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
>> - down_read(&mm->mmap_sem);
>> - exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end);
>> - up_read(&mm->mmap_sem);
>> + status = down_read_killable(&mm->mmap_sem);
>> + if (!status) {
>> + exact_vma_exists = !!find_exact_vma(mm, vm_start,
>> + vm_end);
>> + up_read(&mm->mmap_sem);
>> + }
>> }
>>
>> mmput(mm);
>> @@ -2010,8 +2013,11 @@ static int map_files_get_link(struct dentry *dentry, struct path *path)
>> if (rc)
>> goto out_mmput;
>>
>> + rc = down_read_killable(&mm->mmap_sem);
>> + if (rc)
>> + goto out_mmput;
>> +
>> rc = -ENOENT;
>> - down_read(&mm->mmap_sem);
>> vma = find_exact_vma(mm, vm_start, vm_end);
>> if (vma && vma->vm_file) {
>> *path = vma->vm_file->f_path;
>> @@ -2107,7 +2113,10 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
>> if (!mm)
>> goto out_put_task;
>>
>> - down_read(&mm->mmap_sem);
>> + result = ERR_PTR(-EINTR);
>> + if (down_read_killable(&mm->mmap_sem))
>> + goto out_put_mm;
>> +
>
> result = ERR_PTR(-ENOENT);
>
>> vma = find_exact_vma(mm, vm_start, vm_end);
>> if (!vma)
>> goto out_no_vma;
>> @@ -2118,6 +2127,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
>>
>> out_no_vma:
>> up_read(&mm->mmap_sem);
>> +out_put_mm:
>> mmput(mm);
>> out_put_task:
>> put_task_struct(task);
>> @@ -2160,7 +2170,12 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
>> mm = get_task_mm(task);
>> if (!mm)
>> goto out_put_task;
>> - down_read(&mm->mmap_sem);
>> +
>> + ret = down_read_killable(&mm->mmap_sem);
>> + if (ret) {
>> + mmput(mm);
>> + goto out_put_task;
>> + }
>>
>> nr_files = 0;
>>
next prev parent reply other threads:[~2019-06-13 16:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-09 10:08 [PATCH v2 0/6] mm: use down_read_killable for locking mmap_sem in proc Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 1/6] proc: use down_read_killable mmap_sem for /proc/pid/maps Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 2/6] proc: use down_read_killable mmap_sem for /proc/pid/smaps_rollup Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 3/6] proc: use down_read_killable mmap_sem for /proc/pid/pagemap Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 4/6] proc: use down_read_killable mmap_sem for /proc/pid/clear_refs Konstantin Khlebnikov
2019-06-09 10:09 ` [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files Konstantin Khlebnikov
2019-06-12 23:14 ` Andrei Vagin
2019-06-13 0:04 ` Andrew Morton
2019-06-13 6:48 ` Cyrill Gorcunov
2019-06-13 8:15 ` Konstantin Khlebnikov [this message]
2019-06-13 20:32 ` Andrei Vagin
2019-06-09 10:09 ` [PATCH v2 6/6] mm: use down_read_killable for locking mmap_sem in access_remote_vm Konstantin Khlebnikov
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