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    zram: support REQ_DISCARD · f4659d8e
    Joonsoo Kim 提交于
    zram is ram based block device and can be used by backend of filesystem.
    When filesystem deletes a file, it normally doesn't do anything on data
    block of that file.  It just marks on metadata of that file.  This
    behavior has no problem on disk based block device, but has problems on
    ram based block device, since we can't free memory used for data block.
    To overcome this disadvantage, there is REQ_DISCARD functionality.  If
    block device support REQ_DISCARD and filesystem is mounted with discard
    option, filesystem sends REQ_DISCARD to block device whenever some data
    blocks are discarded.  All we have to do is to handle this request.
    
    This patch implements to flag up QUEUE_FLAG_DISCARD and handle this
    REQ_DISCARD request.  With it, we can free memory used by zram if it isn't
    used.
    
    [akpm@linux-foundation.org: tweak comments]
    Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Nitin Gupta <ngupta@vflare.org>
    Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Cc: Jerome Marchand <jmarchan@redhat.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    f4659d8e
zram_drv.c 23.7 KB