• Martin K. Petersen's avatar
    libata: Whitelist SSDs that are known to properly return zeroes after TRIM · e61f7d1c
    Martin K. Petersen authored
    As defined, the DRAT (Deterministic Read After Trim) and RZAT (Return
    Zero After Trim) flags in the ATA Command Set are unreliable in the
    sense that they only define what happens if the device successfully
    executed the DSM TRIM command. TRIM is only advisory, however, and the
    device is free to silently ignore all or parts of the request.
    
    In practice this renders the DRAT and RZAT flags completely useless and
    because the results are unpredictable we decided to disable discard in
    MD for 3.18 to avoid the risk of data corruption.
    
    Hardware vendors in the real world obviously need better guarantees than
    what the standards bodies provide. Unfortuntely those guarantees are
    encoded in product requirements documents rather than somewhere we can
    key off of them programatically. So we are compelled to disabling
    discard_zeroes_data for all devices unless we explicitly have data to
    support whitelisting them.
    
    This patch whitelists SSDs from a few of the main vendors. None of the
    whitelists are based on written guarantees. They are purely based on
    empirical evidence collected from internal and external users that have
    tested or qualified these drives in RAID deployments.
    
    The whitelist is only meant as a starting point and is by no means
    comprehensive:
    
       - All intel SSD models except for 510
       - Micron M5?0/M600
       - Samsung SSDs
       - Seagate SSDs
    Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    e61f7d1c
libata-scsi.c 106 KB