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@yandex-team.ru> Reviewed-by: Roman Gushchin <guro@fb.com> Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com> Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Koutný <mkoutny@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1547,7 +1547,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
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/* overflow ? */
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if (end < start_vaddr || end > end_vaddr)
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end = end_vaddr;
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down_read(&mm->mmap_sem);
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ret = down_read_killable(&mm->mmap_sem);
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if (ret)
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goto out_free;
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ret = walk_page_range(start_vaddr, end, &pagemap_walk);
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up_read(&mm->mmap_sem);
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start_vaddr = end;
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