From 98262f2762f0067375f83824d81ea929e37e6bfe Mon Sep 17 00:00:00 2001 From: "Martin K. Petersen" Date: Thu, 3 Dec 2009 09:24:48 +0100 Subject: block: Allow devices to indicate whether discarded blocks are zeroed The discard ioctl is used by mkfs utilities to clear a block device prior to putting metadata down. However, not all devices return zeroed blocks after a discard. Some drives return stale data, potentially containing old superblocks. It is therefore important to know whether discarded blocks are properly zeroed. Both ATA and SCSI drives have configuration bits that indicate whether zeroes are returned after a discard operation. Implement a block level interface that allows this information to be bubbled up the stack and queried via a new block device ioctl. Signed-off-by: Martin K. Petersen Signed-off-by: Jens Axboe --- include/linux/blkdev.h | 14 ++++++++++++++ include/linux/fs.h | 1 + 2 files changed, 15 insertions(+) (limited to 'include') diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index e727f6c44c44..784a919aa0d0 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -322,6 +322,7 @@ struct queue_limits { unsigned char misaligned; unsigned char discard_misaligned; unsigned char no_cluster; + signed char discard_zeroes_data; }; struct request_queue @@ -1150,6 +1151,19 @@ static inline int queue_sector_discard_alignment(struct request_queue *q, & (q->limits.discard_granularity - 1); } +static inline unsigned int queue_discard_zeroes_data(struct request_queue *q) +{ + if (q->limits.discard_zeroes_data == 1) + return 1; + + return 0; +} + +static inline unsigned int bdev_discard_zeroes_data(struct block_device *bdev) +{ + return queue_discard_zeroes_data(bdev_get_queue(bdev)); +} + static inline int queue_dma_alignment(struct request_queue *q) { return q ? q->dma_alignment : 511; diff --git a/include/linux/fs.h b/include/linux/fs.h index 79cea8051736..891f7d642e5c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -304,6 +304,7 @@ struct inodes_stat_t { #define BLKIOOPT _IO(0x12,121) #define BLKALIGNOFF _IO(0x12,122) #define BLKPBSZGET _IO(0x12,123) +#define BLKDISCARDZEROES _IO(0x12,124) #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ #define FIBMAP _IO(0x00,1) /* bmap access */ -- cgit v1.2.3