From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Subject: proc: use down_read_killable mmap_sem for /proc/pid/pagemap Do not remain stuck forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. Link: http://lkml.kernel.org/r/156007493638.3335.4872164955523928492.stgit@buzz 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> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Michal Koutný <mkoutny@xxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/task_mmu.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/proc/task_mmu.c~proc-use-down_read_killable-mmap_sem-for-proc-pid-pagemap +++ a/fs/proc/task_mmu.c @@ -1547,7 +1547,9 @@ static ssize_t pagemap_read(struct file /* overflow ? */ if (end < start_vaddr || end > end_vaddr) end = end_vaddr; - down_read(&mm->mmap_sem); + ret = down_read_killable(&mm->mmap_sem); + if (ret) + goto out_free; ret = walk_page_range(start_vaddr, end, &pagemap_walk); up_read(&mm->mmap_sem); start_vaddr = end; _
