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    procfs task exe symlink · 925d1c40
    Matt Helsley 提交于
    The kernel implements readlink of /proc/pid/exe by getting the file from
    the first executable VMA.  Then the path to the file is reconstructed and
    reported as the result.
    
    Because of the VMA walk the code is slightly different on nommu systems.
    This patch avoids separate /proc/pid/exe code on nommu systems.  Instead of
    walking the VMAs to find the first executable file-backed VMA we store a
    reference to the exec'd file in the mm_struct.
    
    That reference would prevent the filesystem holding the executable file
    from being unmounted even after unmapping the VMAs.  So we track the number
    of VM_EXECUTABLE VMAs and drop the new reference when the last one is
    unmapped.  This avoids pinning the mounted filesystem.
    
    [akpm@linux-foundation.org: improve comments]
    [yamamoto@valinux.co.jp: fix dup_mmap]
    Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
    Cc: Oleg Nesterov <oleg@tv-sign.ru>
    Cc: David Howells <dhowells@redhat.com>
    Cc:"Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Hugh Dickins <hugh@veritas.com>
    Signed-off-by: NYAMAMOTO Takashi <yamamoto@valinux.co.jp>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    925d1c40
mmap.c 58.5 KB