On Thu, Jun 13, 2019 at 1:15 AM Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> wrote: > > 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. =) I remember Mike was trying to add the CRIU test suite into kernel-ci, but it looks like this ended up with nothing. The good thing here is that we have our own kernel-ci: https://travis-ci.org/avagin/linux/builds Travis-CI doesn't allow to replace the kernel, so we use CRIU to dump/restore a ssh session and travis doesn't notice when we kexec a new kernel. > > > > > 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@xxxxxxxxxxxxxx> > >> Reviewed-by: Roman Gushchin <guro@xxxxxx> > >> Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx> > >> Reviewed-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > > > > It was nice to see all four of you in one place :). > > > >> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > >> --- > >> 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; > >>
