On 11/20/2009 09:45 PM, Martin K. Petersen wrote:
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.
Signed-off-by: Martin K. Petersen<martin.petersen@xxxxxxxxxx>
---
block/blk-settings.c | 2 ++
block/blk-sysfs.c | 11 +++++++++++
include/linux/blkdev.h | 1 +
3 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 7f986ca..1027e30 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -100,6 +100,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->discard_granularity = 0;
lim->discard_alignment = 0;
lim->discard_misaligned = 0;
+ lim->discard_zeroes_data = -1;
Did you mean to set this to -1 ?
ric
lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY>> PAGE_SHIFT);
lim->alignment_offset = 0;
@@ -543,6 +544,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->io_min = max(t->io_min, b->io_min);
t->no_cluster |= b->no_cluster;
+ t->discard_zeroes_data&= b->discard_zeroes_data;
/* Bottom device offset aligned? */
if (offset&&
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 3147145..1f1d2b6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -136,6 +136,11 @@ static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
return queue_var_show(q->limits.max_discard_sectors<< 9, page);
}
+static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(q->limits.discard_zeroes_data == 1 ? 1 : 0, page);
+}
+
static ssize_t
queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
{
@@ -313,6 +318,11 @@ static struct queue_sysfs_entry queue_discard_max_entry = {
.show = queue_discard_max_show,
};
+static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
+ .attr = {.name = "discard_zeroes_data", .mode = S_IRUGO },
+ .show = queue_discard_zeroes_data_show,
+};
+
static struct queue_sysfs_entry queue_nonrot_entry = {
.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
.show = queue_nonrot_show,
@@ -350,6 +360,7 @@ static struct attribute *default_attrs[] = {
&queue_io_opt_entry.attr,
&queue_discard_granularity_entry.attr,
&queue_discard_max_entry.attr,
+ &queue_discard_zeroes_data_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3b67221..e605945 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
--
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