• Al Viro's avatar
    9p: ->evict_inode() should kick out ->i_data, not ->i_mapping · 4ad78628
    Al Viro authored
    For block devices the pagecache is associated with the inode
    on bdevfs, not with the aliasing ones on the mountable filesystems.
    The latter have its own ->i_data empty and ->i_mapping pointing
    to the (unique per major/minor) bdevfs inode.  That guarantees
    cache coherence between all block device inodes with the same
    device number.
    
    Eviction of an alias inode has no business trying to evict the
    pages belonging to bdevfs one; moreover, ->i_mapping is only
    safe to access when the thing is opened.  At the time of
    ->evict_inode() the victim is definitely *not* opened.  We are
    about to kill the address space embedded into struct inode
    (inode->i_data) and that's what we need to empty of any pages.
    
    9p instance tries to empty inode->i_mapping instead, which is
    both unsafe and bogus - if we have several device nodes with
    the same device number in different places, closing one of them
    should not try to empty the (shared) page cache.
    
    Fortunately, other instances in the tree are OK; they are
    evicting from &inode->i_data instead, as 9p one should.
    
    Cc: stable@vger.kernel.org # v2.6.32+, ones prior to 2.6.36 need only half of that
    Reported-by: default avatar"Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
    Tested-by: default avatar"Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    4ad78628
vfs_inode.c 33.2 KB