Author: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx> Date: Wed Feb 1 20:42:02 2017 -0200 sd: wait for slow devices on shutdown path Wait 1s during suspend/shutdown for the device to settle after we issue the STOP command. Otherwise we race ATA SSDs to powerdown, possibly causing damage to FLASH/data and even bricking the device. This is an experimental patch, there are likely better ways of doing this that don't punish non-SSDs. Signed-off-by: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 4e08d1cd..3c6d5d3 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -3230,6 +3230,38 @@ static int sd_start_stop_device(struct scsi_disk *sdkp, int start) res = 0; } + /* + * Wait for slow devices that signal they have fully entered + * the stopped state before they actully did it. + * + * This behavior is apparently allowed per-spec for ATA + * devices, and our SAT layer does not account for it. + * Thus, on return, the device might still be in the process + * of entering STANDBY state. + * + * Worse, apparently the ATA spec also says the unit should + * return that it is already in STANDBY state *while still + * entering that state*. + * + * SSDs absolutely depend on receiving a STANDBY IMMEDIATE + * command prior to power off for a clean shutdown (and + * likely we don't want to send them *anything else* in- + * between either, to be on the safe side). + * + * As things stand, we are racing the SSD's firmware. If it + * finishes first, nothing bad happens. If it doesn't, we + * cut power while it is still saving metadata, and not only + * this will cause extra FLASH wear (and maybe even damage + * some cells), it also has a non-zero chance of bricking the + * SSD. + * + * Issue reported on Intel, Crucial and Micron SSDs. + * Issue can be detected by S.M.A.R.T. signaling unexpected + * power cuts. + */ + if (!res && !start) + msleep(1000); + /* SCSI error codes must not go to the generic layer */ if (res) return -EIO; -- Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html