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    sysfs: refill attribute buffer when reading from offset 0 · 2424b5dd
    Dan Williams 提交于
    Requiring userspace to close and re-open sysfs attributes has been the
    policy since before 2.6.12.  It allows userspace to get a consistent
    snapshot of kernel state and consume it with incremental reads and seeks.
    
    Now, if the file position is zero the kernel assumes userspace wants to see
    the new value.  The application for this change is to allow a userspace
    RAID metadata handler to check the state of an array without causing any
    memory allocations.  Thus not causing writeback to a raid array that might
    be blocked waiting for userspace to take action.
    
    Cc: Neil Brown <neilb@suse.de>
    Acked-by: NTejun Heo <htejun@gmail.com>
    Signed-off-by: NDan Williams <dan.j.williams@intel.com>
    Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
    
    2424b5dd
sysfs.txt 10.1 KB