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Message-ID: <yq1wri6zel9.fsf@sermon.lab.mkp.net>
Date: Wed, 04 May 2011 11:10:26 -0400
From: "Martin K. Petersen" <martin.petersen@...cle.com>
To: Lukas Czerner <lczerner@...hat.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>,
Christoph Hellwig <hch@...radead.org>,
device-mapper development <dm-devel@...hat.com>,
Alasdair G Kergon <agk@...hat.com>, sandeen@...hat.com,
Mike Snitzer <snitzer@...hat.com>, DarkNovaNick@...il.com,
linux-lvm@...hat.com, linux-ext4@...r.kernel.org
Subject: Re: [dm-devel] do not disable ext4 discards on first discard failure? [was: Re: dm snapshot: ignore discards issued to the snapshot-origin target]
>>>>> "Lukas" == Lukas Czerner <lczerner@...hat.com> writes:
Lukas> Nevertheless there is something weird going on, because even when
Lukas> I create striped volume I get this:
Could you please try the following patch? It has a bunch of small tweaks
to the discard stack in it. I'll split it up before posting for real but
I'd like to know if it fixes your issue...
block/libata/scsi: Various logical block provisioning fixes
- Add sysfs documentation for the discard topology parameters
- Fix discard stacking problem
- Switch our libata SAT over to using the WRITE SAME limits
- UNMAP alignment needs to be converted to bytes
- Only report alignment and zeroes_data if the device supports discard
Reported-by: Lukas Czerner <lczerner@...hat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 4873c75..c1eb41c 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -142,3 +142,67 @@ Description:
with the previous I/O request are enabled. When set to 2,
all merge tries are disabled. The default value is 0 -
which enables all types of merge tries.
+
+What: /sys/block/<disk>/discard_alignment
+Date: May 2011
+Contact: Martin K. Petersen <martin.petersen@...cle.com>
+Description:
+ Devices that support discard functionality may
+ internally allocate space in units that are bigger than
+ the exported logical block size. The discard_alignment
+ parameter indicates how many bytes the beginning of the
+ device is offset from the internal allocation unit's
+ natural alignment.
+
+What: /sys/block/<disk>/<partition>/discard_alignment
+Date: May 2011
+Contact: Martin K. Petersen <martin.petersen@...cle.com>
+Description:
+ Devices that support discard functionality may
+ internally allocate space in units that are bigger than
+ the exported logical block size. The discard_alignment
+ parameter indicates how many bytes the beginning of the
+ partition is offset from the internal allocation unit's
+ natural alignment.
+
+What: /sys/block/<disk>/queue/discard_granularity
+Date: May 2011
+Contact: Martin K. Petersen <martin.petersen@...cle.com>
+Description:
+ Devices that support discard functionality may
+ internally allocate space using units that are bigger
+ than the logical block size. The discard_granularity
+ parameter indicates the size of the internal allocation
+ unit in bytes if reported by the device. Otherwise the
+ discard_granularity will be set to match the device's
+ physical block size. A discard_granularity of 0 means
+ that the device does not support discard functionality.
+
+What: /sys/block/<disk>/queue/discard_max_bytes
+Date: May 2011
+Contact: Martin K. Petersen <martin.petersen@...cle.com>
+Description:
+ Devices that support discard functionality may have
+ internal limits on the number of bytes that can be
+ trimmed or unmapped in a single operation. Some storage
+ protocols also have inherent limits on the number of
+ blocks that can be described in a single command. The
+ discard_max_bytes parameter is set by the device driver
+ to the maximum number of bytes that can be discarded in
+ a single operation. Discard requests issued to the
+ device must not exceed this limit. A discard_max_bytes
+ value of 0 means that the device does not support
+ discard functionality.
+
+What: /sys/block/<disk>/queue/discard_zeroes_data
+Date: May 2011
+Contact: Martin K. Petersen <martin.petersen@...cle.com>
+Description:
+ Devices that support discard functionality may return
+ stale or random data when a previously discarded block
+ is read back. This can cause problems if the filesystem
+ expects discarded blocks to be explicitly cleared. If a
+ device reports that it deterministically returns zeroes
+ when a discarded area is read the discard_zeroes_data
+ parameter will be set to one. Otherwise it will be 0 and
+ the result of reading a discarded area is undefined.
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 1fa7692..42d3bf5 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -120,7 +120,7 @@ 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;
+ lim->discard_zeroes_data = 1;
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;
@@ -166,6 +166,7 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
blk_set_default_limits(&q->limits);
blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
+ q->limits.discard_zeroes_data = 0;
/*
* by default assume old behaviour and bounce for any highmem page
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index e2f57e9e..30ea95f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2138,7 +2138,7 @@ static unsigned int ata_scsiop_inq_b0(struct ata_scsi_args *args, u8 *rbuf)
* with the unmap bit set.
*/
if (ata_id_has_trim(args->id)) {
- put_unaligned_be32(65535 * 512 / 8, &rbuf[20]);
+ put_unaligned_be64(65535 * 512 / 8, &rbuf[36]);
put_unaligned_be32(1, &rbuf[28]);
}
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bd0806e..cc081dd 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -490,7 +490,8 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
unsigned int max_blocks = 0;
q->limits.discard_zeroes_data = sdkp->lbprz;
- q->limits.discard_alignment = sdkp->unmap_alignment;
+ q->limits.discard_alignment = sdkp->unmap_alignment *
+ (logical_block_size >> 9);
q->limits.discard_granularity =
max(sdkp->physical_block_size,
sdkp->unmap_granularity * logical_block_size);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2ad95fa..1416e3c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -257,7 +257,7 @@ struct queue_limits {
unsigned char misaligned;
unsigned char discard_misaligned;
unsigned char cluster;
- signed char discard_zeroes_data;
+ unsigned char discard_zeroes_data;
};
struct request_queue
@@ -1066,13 +1066,16 @@ static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector
{
unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);
+ if (!lim->max_discard_sectors)
+ return 0;
+
return (lim->discard_granularity + lim->discard_alignment - alignment)
& (lim->discard_granularity - 1);
}
static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)
{
- if (q->limits.discard_zeroes_data == 1)
+ if (q->limits.max_discard_sectors && q->limits.discard_zeroes_data == 1)
return 1;
return 0;
--
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