From: Konstantin Khlebnikov <khlebni...@yandex-team.ru> [ Upstream commit cd9e2bb8271c971d9f37c722be2616c7f8ba0664 ]
Do not remain stuck forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. It seems ->d_revalidate() could return any error (except ECHILD) to abort validation and pass error as result of lookup sequence. [a...@linux-foundation.org: fix proc_map_files_lookup() return value, per Andrei] Link: http://lkml.kernel.org/r/156007493995.3335.9595044802115356911.stgit@buzz Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru> Reviewed-by: Roman Gushchin <g...@fb.com> Reviewed-by: Cyrill Gorcunov <gorcu...@gmail.com> Reviewed-by: Kirill Tkhai <ktk...@virtuozzo.com> Acked-by: Michal Hocko <mho...@suse.com> Cc: Alexey Dobriyan <adobri...@gmail.com> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: Matthew Wilcox <wi...@infradead.org> Cc: Michal Koutný <mkou...@suse.com> Cc: Oleg Nesterov <o...@redhat.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Sasha Levin <sas...@kernel.org> --- fs/proc/base.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 255f6754c70d..03517154fe0f 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 +2113,11 @@ 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 +2128,7 @@ 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 +2171,12 @@ 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; -- 2.20.1
