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    Subject[PATCH 5 of 7] block: Block/request layer data integrity support
    Date
    From
    10 files changed, 849 insertions(+)
    Documentation/block/data-integrity.txt | 327 +++++++++++++++++++++++++++
    block/Kconfig | 12
    block/Makefile | 1
    block/blk-core.c | 7
    block/blk-integrity.c | 385 ++++++++++++++++++++++++++++++++
    block/blk-merge.c | 3
    block/blk.h | 8
    block/elevator.c | 6
    include/linux/blkdev.h | 97 ++++++++
    include/linux/genhd.h | 3


    Support for merging and mapping bio integrity metadata.

    Block device integrity type registration.

    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

    ---

    diff -r f2ae9d5bce4c -r 5be7c534c954 Documentation/block/data-integrity.txt
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/Documentation/block/data-integrity.txt Sat Jun 07 00:45:15 2008 -0400
    @@ -0,0 +1,327 @@
    +----------------------------------------------------------------------
    +1. INTRODUCTION
    +
    +Modern filesystems feature checksumming of data and metadata to
    +protect against data corruption. However, the detection of the
    +corruption is done at read time which could potentially be months
    +after the data was written. At that point the original data that the
    +application tried to write is most likely lost.
    +
    +The solution is to ensure that the disk is actually storing what the
    +application meant it to. Recent additions to both the SCSI family
    +protocols (SBC Data Integrity Field, SCC protection proposal) as well
    +as SATA/T13 (External Path Protection) try to remedy this by adding
    +support for appending integrity metadata to an I/O. The integrity
    +metadata (or protection information in SCSI terminology) includes a
    +checksum for each sector as well as an incrementing counter that
    +ensures the individual sectors are written in the right order. And
    +for some protection schemes also that the I/O is written to the right
    +place on disk.
    +
    +Current storage controllers and devices implement various protective
    +measures, for instance checksumming and scrubbing. But these
    +technologies are working in their own isolated domains or at best
    +between adjacent nodes in the I/O path. The interesting thing about
    +DIF and the other integrity extensions is that the protection format
    +is well defined and every node in the I/O path can verify the
    +integrity of the I/O and reject it if corruption is detected. This
    +allows not only corruption prevention but also isolation of the point
    +of failure.
    +
    +----------------------------------------------------------------------
    +2. THE DATA INTEGRITY EXTENSIONS
    +
    +As written, the protocol extensions only protect the path between
    +controller and storage device. However, many controllers actually
    +allow the operating system to interact with the integrity metadata
    +(IMD). We have been working with several FC/SAS HBA vendors to enable
    +the protection information to be transferred to and from their
    +controllers.
    +
    +The SCSI Data Integrity Field works by appending 8 bytes of protection
    +information to each sector. The data + integrity metadata is stored
    +in 520 byte sectors on disk. Data + IMD are interleaved when
    +transferred between the controller and target. The T13 proposal is
    +similar.
    +
    +Because it is highly inconvenient for operating systems to deal with
    +520 (and 4104) byte sectors, we approached several HBA vendors and
    +encouraged them to allow separation of the data and integrity metadata
    +scatter-gather lists.
    +
    +The controller will interleave the buffers on write and split them on
    +read. This means that the Linux can DMA the data buffers to and from
    +host memory without changes to the page cache.
    +
    +Also, the 16-bit CRC checksum mandated by both the SCSI and SATA specs
    +is somewhat heavy to compute in software. Benchmarks found that
    +calculating this checksum had a significant impact on system
    +performance for a number of workloads. Some controllers allow a
    +lighter-weight checksum to be used when interfacing with the operating
    +system. Emulex, for instance, supports the TCP/IP checksum instead.
    +The IP checksum received from the OS is converted to the 16-bit CRC
    +when writing and vice versa. This allows the integrity metadata to be
    +generated by Linux or the application at very low cost (comparable to
    +software RAID5).
    +
    +The IP checksum is weaker than the CRC in terms of detecting bit
    +errors. However, the strength is really in the separation of the data
    +buffers and the integrity metadata. These two distinct buffers much
    +match up for an I/O to complete.
    +
    +The separation of the data and integrity metadata buffers as well as
    +the choice in checksums is referred to as the Data Integrity
    +Extensions. As these extensions are outside the scope of the protocol
    +bodies (T10, T13), Oracle and its partners are trying to standardize
    +them within the Storage Networking Industry Association.
    +
    +----------------------------------------------------------------------
    +3. KERNEL CHANGES
    +
    +The data integrity framework in Linux enables protection information
    +to be pinned to I/Os and sent to/received from controllers that
    +support it.
    +
    +The advantage to the integrity extensions in SCSI and SATA is that
    +they enable us to protect the entire path from application to storage
    +device. However, at the same time this is also the biggest
    +disadvantage. It means that the protection information must be in a
    +format that can be understood by the disk.
    +
    +Generally Linux/POSIX applications are agnostic to the intricacies of
    +the storage devices they are accessing. The virtual filesystem switch
    +and the block layer make things like hardware sector size and
    +transport protocols completely transparent to the application.
    +
    +However, this level of detail is required when preparing the
    +protection information to send to a disk. Consequently, the very
    +concept of an end-to-end protection scheme is a layering violation.
    +It is completely unreasonable for an application to be aware whether
    +it is accessing a SCSI or SATA disk.
    +
    +The data integrity support implemented in Linux attempts to hide this
    +from the application. As far as the application (and to some extent
    +the kernel) is concerned, the integrity metadata is opaque information
    +that's attached to the I/O.
    +
    +The current implementation allows the block layer to automatically
    +generate the protection information for any I/O. Eventually the
    +intent is to move the integrity metadata calculation to userspace for
    +user data. Metadata and other I/O that originates within the kernel
    +will still use the automatic generation interface.
    +
    +Some storage devices allow each hardware sector to be tagged with a
    +16-bit value. The owner of this tag space is the owner of the block
    +device. I.e. the filesystem in most cases. The filesystem can use
    +this extra space to tag sectors as they see fit. Because the tag
    +space is limited, the block interface allows tagging bigger chunks by
    +way of interleaving. This way, 8*16 bits of information can be
    +attached to a typical 4KB filesystem block.
    +
    +This also means that applications such as fsck and mkfs will need
    +access to manipulate the tags from user space. A passthrough
    +interface for this is being worked on.
    +
    +
    +----------------------------------------------------------------------
    +4. BLOCK LAYER IMPLEMENTATION DETAILS
    +
    +4.1 BIO
    +
    +The data integrity patches add a new field to struct bio when
    +CONFIG_BLK_DEV_INTEGRITY is enabled. bio->bi_integrity is a pointer
    +to a struct bip which contains the bio integrity payload. Essentially
    +a bip is a trimmed down struct bio which holds a bio_vec containing
    +the integrity metadata and the required housekeeping information (bvec
    +pool, vector count, etc.)
    +
    +A kernel subsystem can enable data integrity protection on a bio by
    +calling bio_integrity_alloc(bio). This will allocate and attach the
    +bip to the bio.
    +
    +Individual pages containing integrity metadata can subsequently be
    +attached using bio_integrity_add_page().
    +
    +bio_free() will automatically free the bip.
    +
    +
    +4.2 BLOCK DEVICE
    +
    +Because the format of the protection data is tied to the physical
    +disk, each block device has been extended with a block integrity
    +profile (struct blk_integrity). This optional profile is registered
    +with the block layer using blk_integrity_register().
    +
    +The profile contains callback functions for generating and verifying
    +the protection data, as well as getting and setting application tags.
    +The profile also contains a few constants to aid in completing,
    +merging and splitting the integrity metadata.
    +
    +Layered block devices will need to pick a profile that's appropriate
    +for all subdevices. blk_integrity_compare() can help with that. DM
    +and MD linear, RAID0 and RAID1 are currently supported. RAID4/5/6
    +will require extra work due to the application tag.
    +
    +
    +----------------------------------------------------------------------
    +5.0 BLOCK LAYER INTEGRITY API
    +
    +5.1 NORMAL FILESYSTEM
    +
    + The normal filesystem is unaware that the underlying block device
    + is capable of sending/receiving integrity metadata. The IMD will
    + be automatically generated by the block layer at submit_bio() time
    + in case of a WRITE. A READ request will cause the I/O integrity
    + to be verified upon completion.
    +
    + IMD generation and verification can be toggled using the
    +
    + /sys/class/block/<bdev>/integrity/write_generate
    +
    + and
    +
    + /sys/class/block/<bdev>/integrity/read_verify
    +
    + flags.
    +
    +
    +5.2 INTEGRITY-AWARE FILESYSTEM
    +
    + A filesystem that is integrity-aware can prepare I/Os with IMD
    + attached. It can also use the application tag space if this is
    + supported by the block device.
    +
    +
    + int bdev_integrity_enabled(block_device, int rw);
    +
    + bdev_integrity_enabled() will return 1 if the block device
    + supports integrity metadata transfer for the data direction
    + specified in 'rw'.
    +
    + bdev_integrity_enabled() honors the write_generate and
    + read_verify flags in sysfs and will respond accordingly.
    +
    +
    + int bio_integrity_prep(bio);
    +
    + To generate IMD for WRITE and to set up buffers for READ, the
    + filesystem must call bio_integrity_prep(bio).
    +
    + Prior to calling this function, the bio data direction and start
    + sector must be set, and the bio should have all data pages
    + added. It is up to the caller to ensure that the bio does not
    + change while I/O is in progress.
    +
    + bio_integrity_prep() should only be called if
    + bio_integrity_enabled() returned 1.
    +
    +
    + int bio_integrity_tag_size(bio);
    +
    + If the filesystem wants to use the application tag space it will
    + first have to find out how much storage space is available.
    + Because tag space is generally limited (usually 2 bytes per
    + sector regardless of sector size), the integrity framework
    + supports interleaving the information between the sectors in an
    + I/O.
    +
    + Filesystems can call bio_integrity_tag_size(bio) to find out how
    + many bytes of storage are available for that particular bio.
    +
    + Another option is bdev_get_tag_size(block_device) which will
    + return the number of available bytes per hardware sector.
    +
    +
    + int bio_integrity_set_tag(bio, void *tag_buf, len);
    +
    + After a successful return from bio_integrity_prep(),
    + bio_integrity_set_tag() can be used to attach an opaque tag
    + buffer to a bio. Obviously this only makes sense if the I/O is
    + a WRITE.
    +
    +
    + int bio_integrity_get_tag(bio, void *tag_buf, len);
    +
    + Similarly, at READ I/O completion time the filesystem can
    + retrieve the tag buffer using bio_integrity_get_tag().
    +
    +
    +6.3 PASSING EXISTING INTEGRITY METADATA
    +
    + Filesystems that either generate their own integrity metadata or
    + are capable of transferring IMD from user space can use the
    + following calls:
    +
    +
    + struct bip * bio_integrity_alloc(bio, gfp_mask, nr_pages);
    +
    + Allocates the bio integrity payload and hangs it off of the bio.
    + nr_pages indicate how many pages of protection data need to be
    + stored in the integrity bio_vec list (similar to bio_alloc()).
    +
    + The integrity payload will be freed at bio_free() time.
    +
    +
    + int bio_integrity_add_page(bio, page, len, offset);
    +
    + Attaches a page containing integrity metadata to an existing
    + bio. The bio must have an existing bip,
    + i.e. bio_integrity_alloc() must have been called. For a WRITE,
    + the integrity metadata in the pages must be in a format
    + understood by the target device with the notable exception that
    + the sector numbers will be remapped as the request traverses the
    + I/O stack. This implies that the pages added using this call
    + will be modified during I/O! The first reference tag in the
    + integrity metadata must have a value of bip->bip_sector.
    +
    + Pages can be added using bio_integrity_add_page() as long as
    + there is room in the bip bio_vec array (nr_pages).
    +
    + Upon completion of a READ operation, the attached pages will
    + contain the integrity metadata received from the storage device.
    + It is up to the receiver to process them and verify data
    + integrity upon completion.
    +
    +
    +6.4 REGISTERING A BLOCK DEVICE AS CAPABLE OF EXCHANGING INTEGRITY
    + METADATA
    +
    + To enable integrity exchange on a block device the gendisk must be
    + registered as capable:
    +
    + int blk_integrity_register(gendisk, blk_integrity);
    +
    + The blk_integrity struct is a template and should contain the
    + following:
    +
    + static struct blk_integrity my_profile = {
    + .name = "STANDARDSBODY-TYPE-VARIANT-CSUM",
    + .generate_fn = my_generate_fn,
    + .verify_fn = my_verify_fn,
    + .get_tag_fn = my_get_tag_fn,
    + .set_tag_fn = my_set_tag_fn,
    + .tuple_size = sizeof(struct my_tuple_size),
    + .tag_size = <tag bytes per hw sector>,
    + };
    +
    + 'name' is a text string which will be visible in sysfs. This is
    + part of the userland API so chose it carefully and never change
    + it. The format is standards body-type-variant.
    + E.g. T10-DIF-TYPE1-IP or T13-EPP-0-CRC.
    +
    + 'generate_fn' generates appropriate integrity metadata (for WRITE).
    +
    + 'verify_fn' verifies that the data buffer matches the integrity
    + metadata.
    +
    + 'tuple_size' must be set to match the size of the integrity
    + metadata per sector. I.e. 8 for DIF and EPP.
    +
    + 'tag_size' must be set to identify how many bytes of tag space
    + are available per hardware sector. For DIF this is either 2 or
    + 0 depending on the value of the Control Mode Page ATO bit.
    +
    + See 6.2 for a description of get_tag_fn and set_tag_fn.
    +
    +----------------------------------------------------------------------
    +2007-12-24 Martin K. Petersen <martin.petersen@oracle.com>
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/Kconfig
    --- a/block/Kconfig Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/Kconfig Sat Jun 07 00:45:15 2008 -0400
    @@ -81,6 +81,18 @@

    If unsure, say N.

    +config BLK_DEV_INTEGRITY
    + bool "Block layer data integrity support"
    + ---help---
    + Some storage devices allow extra information to be
    + stored/retrieved to help protect the data. The block layer
    + data integrity option provides hooks which can be used by
    + filesystems to ensure better data integrity.
    +
    + Say yes here if you have a storage device that provides the
    + T10/SCSI Data Integrity Field or the T13/ATA External Path
    + Protection.
    +
    endif # BLOCK

    config BLOCK_COMPAT
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/Makefile
    --- a/block/Makefile Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/Makefile Sat Jun 07 00:45:15 2008 -0400
    @@ -14,3 +14,4 @@

    obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
    obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
    +obj-$(CONFIG_BLK_DEV_INTEGRITY) += blk-integrity.o
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/blk-core.c
    --- a/block/blk-core.c Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/blk-core.c Sat Jun 07 00:45:15 2008 -0400
    @@ -143,6 +143,10 @@

    bio->bi_size -= nbytes;
    bio->bi_sector += (nbytes >> 9);
    +
    + if (bio_integrity(bio))
    + bio_integrity_advance(bio, nbytes);
    +
    if (bio->bi_size == 0)
    bio_endio(bio, error);
    } else {
    @@ -1381,6 +1385,9 @@
    */
    blk_partition_remap(bio);

    + if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
    + goto end_io;
    +
    if (old_sector != -1)
    blk_add_trace_remap(q, bio, old_dev, bio->bi_sector,
    old_sector);
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/blk-integrity.c
    --- /dev/null Thu Jan 01 00:00:00 1970 +0000
    +++ b/block/blk-integrity.c Sat Jun 07 00:45:15 2008 -0400
    @@ -0,0 +1,385 @@
    +/*
    + * blk-integrity.c - Block layer data integrity extensions
    + *
    + * Copyright (C) 2007, 2008 Oracle Corporation
    + * Written by: Martin K. Petersen <martin.petersen@oracle.com>
    + *
    + * This program is free software; you can redistribute it and/or
    + * modify it under the terms of the GNU General Public License version
    + * 2 as published by the Free Software Foundation.
    + *
    + * This program is distributed in the hope that it will be useful, but
    + * WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    + * General Public License for more details.
    + *
    + * You should have received a copy of the GNU General Public License
    + * along with this program; see the file COPYING. If not, write to
    + * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
    + * USA.
    + *
    + */
    +
    +#include <linux/blkdev.h>
    +#include <linux/mempool.h>
    +#include <linux/bio.h>
    +#include <linux/scatterlist.h>
    +
    +#include "blk.h"
    +
    +static struct kmem_cache *integrity_cachep;
    +
    +/**
    + * blk_rq_count_integrity_sg - Count number of integrity scatterlist elements
    + * @rq: request with integrity metadata attached
    + *
    + * Description: Returns the number of elements required in a
    + * scatterlist corresponding to the integrity metadata in a request.
    + */
    +int blk_rq_count_integrity_sg(struct request *rq)
    +{
    + struct bio_vec *iv, *ivprv;
    + struct req_iterator iter;
    + unsigned int segments;
    +
    + ivprv = NULL;
    + segments = 0;
    +
    + rq_for_each_integrity_segment(iv, rq, iter) {
    +
    + if (ivprv && BIOVEC_PHYS_MERGEABLE(ivprv, iv))
    + ;
    + else
    + segments++;
    +
    + ivprv = iv;
    + }
    +
    + return segments;
    +}
    +EXPORT_SYMBOL(blk_rq_count_integrity_sg);
    +
    +/**
    + * blk_rq_map_integrity_sg - Map integrity metadata into a scatterlist
    + * @rq: request with integrity metadata attached
    + * @sglist: target scatterlist
    + *
    + * Description: Map the integrity vectors in request into a
    + * scatterlist. The scatterlist must be big enough to hold all
    + * elements. I.e. sized using blk_rq_count_integrity_sg().
    + */
    +int blk_rq_map_integrity_sg(struct request *rq, struct scatterlist *sglist)
    +{
    + struct bio_vec *iv, *ivprv;
    + struct req_iterator iter;
    + struct scatterlist *sg;
    + unsigned int segments;
    +
    + ivprv = NULL;
    + sg = NULL;
    + segments = 0;
    +
    + rq_for_each_integrity_segment(iv, rq, iter) {
    +
    + if (ivprv) {
    + if (!BIOVEC_PHYS_MERGEABLE(ivprv, iv))
    + goto new_segment;
    +
    + sg->length += iv->bv_len;
    + } else {
    +new_segment:
    + if (!sg)
    + sg = sglist;
    + else {
    + sg->page_link &= ~0x02;
    + sg = sg_next(sg);
    + }
    +
    + sg_set_page(sg, iv->bv_page, iv->bv_len, iv->bv_offset);
    + segments++;
    + }
    +
    + ivprv = iv;
    + }
    +
    + if (sg)
    + sg_mark_end(sg);
    +
    + return segments;
    +}
    +EXPORT_SYMBOL(blk_rq_map_integrity_sg);
    +
    +/**
    + * blk_integrity_compare - Compare integrity profile of two block devices
    + * @b1: Device to compare
    + * @b2: Device to compare
    + *
    + * Description: Meta-devices like DM and MD need to verify that all
    + * sub-devices use the same integrity format before advertising to
    + * upper layers that they can send/receive integrity metadata. This
    + * function can be used to check whether two block devices have
    + * compatible integrity formats.
    + */
    +int blk_integrity_compare(struct block_device *bd1, struct block_device *bd2)
    +{
    + struct blk_integrity *b1 = bd1->bd_disk->integrity;
    + struct blk_integrity *b2 = bd2->bd_disk->integrity;
    +
    + BUG_ON(bd1->bd_disk == NULL);
    + BUG_ON(bd2->bd_disk == NULL);
    +
    + if (!b1 || !b2)
    + return 0;
    +
    + if (b1->sector_size != b2->sector_size) {
    + printk(KERN_ERR "%s: %s/%s sector sz %u != %u\n", __func__,
    + bd1->bd_disk->disk_name, bd2->bd_disk->disk_name,
    + b1->sector_size, b2->sector_size);
    + return -1;
    + }
    +
    + if (b1->tuple_size != b2->tuple_size) {
    + printk(KERN_ERR "%s: %s/%s tuple sz %u != %u\n", __func__,
    + bd1->bd_disk->disk_name, bd2->bd_disk->disk_name,
    + b1->tuple_size, b2->tuple_size);
    + return -1;
    + }
    +
    + if (b1->tag_size && b2->tag_size && (b1->tag_size != b2->tag_size)) {
    + printk(KERN_ERR "%s: %s/%s tag sz %u != %u\n", __func__,
    + bd1->bd_disk->disk_name, bd2->bd_disk->disk_name,
    + b1->tag_size, b2->tag_size);
    + return -1;
    + }
    +
    + if (strcmp(b1->name, b2->name)) {
    + printk(KERN_ERR "%s: %s/%s type %s != %s\n", __func__,
    + bd1->bd_disk->disk_name, bd2->bd_disk->disk_name,
    + b1->name, b2->name);
    + return -1;
    + }
    +
    + return 0;
    +}
    +EXPORT_SYMBOL(blk_integrity_compare);
    +
    +struct integrity_sysfs_entry {
    + struct attribute attr;
    + ssize_t (*show)(struct blk_integrity *, char *);
    + ssize_t (*store)(struct blk_integrity *, const char *, size_t);
    +};
    +
    +static ssize_t integrity_attr_show(struct kobject *kobj, struct attribute *attr,
    + char *page)
    +{
    + struct blk_integrity *bi =
    + container_of(kobj, struct blk_integrity, kobj);
    + struct integrity_sysfs_entry *entry =
    + container_of(attr, struct integrity_sysfs_entry, attr);
    + ssize_t ret = -EIO;
    +
    + if (entry->show)
    + ret = entry->show(bi, page);
    +
    + return ret;
    +}
    +
    +static ssize_t integrity_attr_store(struct kobject *kobj, struct attribute *attr,
    + const char *page, size_t count)
    +{
    + struct blk_integrity *bi =
    + container_of(kobj, struct blk_integrity, kobj);
    + struct integrity_sysfs_entry *entry =
    + container_of(attr, struct integrity_sysfs_entry, attr);
    + ssize_t ret = 0;
    +
    + if (entry->store)
    + ret = entry->store(bi, page, count);
    +
    + return ret;
    +}
    +
    +static ssize_t integrity_format_show(struct blk_integrity *bi, char *page)
    +{
    + if (bi != NULL && bi->name != NULL)
    + return sprintf(page, "%s\n", bi->name);
    + else
    + return sprintf(page, "none\n");
    +}
    +
    +static ssize_t integrity_tag_size_show(struct blk_integrity *bi, char *page)
    +{
    + if (bi != NULL)
    + return sprintf(page, "%u\n", bi->tag_size);
    + else
    + return sprintf(page, "0\n");
    +}
    +
    +static ssize_t integrity_read_store(struct blk_integrity *bi,
    + const char *page, size_t count)
    +{
    + char *p = (char *) page;
    + unsigned long val = simple_strtoul(p, &p, 10);
    +
    + if (val == 1)
    + set_bit(INTEGRITY_FLAG_READ, &bi->flags);
    + else
    + clear_bit(INTEGRITY_FLAG_READ, &bi->flags);
    +
    + return count;
    +}
    +
    +static ssize_t integrity_read_show(struct blk_integrity *bi, char *page)
    +{
    + return sprintf(page, "%d\n",
    + test_bit(INTEGRITY_FLAG_READ, &bi->flags) ? 1 : 0);
    +}
    +
    +static ssize_t integrity_write_store(struct blk_integrity *bi,
    + const char *page, size_t count)
    +{
    + char *p = (char *) page;
    + unsigned long val = simple_strtoul(p, &p, 10);
    +
    + if (val == 1)
    + set_bit(INTEGRITY_FLAG_WRITE, &bi->flags);
    + else
    + clear_bit(INTEGRITY_FLAG_WRITE, &bi->flags);
    +
    + return count;
    +}
    +
    +static ssize_t integrity_write_show(struct blk_integrity *bi, char *page)
    +{
    + return sprintf(page, "%d\n",
    + test_bit(INTEGRITY_FLAG_WRITE, &bi->flags) ? 1 : 0);
    +}
    +
    +static struct integrity_sysfs_entry integrity_format_entry = {
    + .attr = { .name = "format", .mode = S_IRUGO },
    + .show = integrity_format_show,
    +};
    +
    +static struct integrity_sysfs_entry integrity_tag_size_entry = {
    + .attr = { .name = "tag_size", .mode = S_IRUGO },
    + .show = integrity_tag_size_show,
    +};
    +
    +static struct integrity_sysfs_entry integrity_read_entry = {
    + .attr = { .name = "read_verify", .mode = S_IRUGO | S_IWUSR },
    + .show = integrity_read_show,
    + .store = integrity_read_store,
    +};
    +
    +static struct integrity_sysfs_entry integrity_write_entry = {
    + .attr = { .name = "write_generate", .mode = S_IRUGO | S_IWUSR },
    + .show = integrity_write_show,
    + .store = integrity_write_store,
    +};
    +
    +static struct attribute *integrity_attrs[] = {
    + &integrity_format_entry.attr,
    + &integrity_tag_size_entry.attr,
    + &integrity_read_entry.attr,
    + &integrity_write_entry.attr,
    + NULL,
    +};
    +
    +static struct sysfs_ops integrity_ops = {
    + .show = &integrity_attr_show,
    + .store = &integrity_attr_store,
    +};
    +
    +static int __init blk_dev_integrity_init(void)
    +{
    + integrity_cachep = kmem_cache_create("blkdev_integrity",
    + sizeof(struct blk_integrity),
    + 0, SLAB_PANIC, NULL);
    + return 0;
    +}
    +subsys_initcall(blk_dev_integrity_init);
    +
    +static void blk_integrity_release(struct kobject *kobj)
    +{
    + struct blk_integrity *bi =
    + container_of(kobj, struct blk_integrity, kobj);
    +
    + kmem_cache_free(integrity_cachep, bi);
    +}
    +
    +static struct kobj_type integrity_ktype = {
    + .default_attrs = integrity_attrs,
    + .sysfs_ops = &integrity_ops,
    + .release = blk_integrity_release,
    +};
    +
    +/**
    + * blk_integrity_register - Register a gendisk as being integrity-capable
    + * @disk: struct gendisk pointer to make integrity-aware
    + * @template: integrity profile
    + *
    + * Description: When a device needs to advertise itself as being able
    + * to send/receive integrity metadata it must use this function to
    + * register the capability with the block layer. The template is a
    + * blk_integrity struct with values appropriate for the underlying
    + * hardware. See Documentation/block/data-integrity.txt.
    + */
    +int blk_integrity_register(struct gendisk *disk, struct blk_integrity *template)
    +{
    + struct blk_integrity *bi;
    +
    + BUG_ON(disk == NULL);
    + BUG_ON(template == NULL);
    +
    + if (disk->integrity == NULL) {
    + bi = kmem_cache_alloc(integrity_cachep, GFP_KERNEL | __GFP_ZERO);
    + if (!bi)
    + return -1;
    +
    + if (kobject_init_and_add(&bi->kobj, &integrity_ktype,
    + &disk->dev.kobj, "%s", "integrity"))
    + return -1;
    +
    + kobject_uevent(&bi->kobj, KOBJ_ADD);
    +
    + set_bit(INTEGRITY_FLAG_READ, &bi->flags);
    + set_bit(INTEGRITY_FLAG_WRITE, &bi->flags);
    + bi->sector_size = disk->queue->hardsect_size;
    + disk->integrity = bi;
    + } else
    + bi = disk->integrity;
    +
    + /* Use the provided profile as template */
    + bi->name = template->name;
    + bi->generate_fn = template->generate_fn;
    + bi->verify_fn = template->verify_fn;
    + bi->tuple_size = template->tuple_size;
    + bi->set_tag_fn = template->set_tag_fn;
    + bi->get_tag_fn = template->get_tag_fn;
    + bi->tag_size = template->tag_size;
    +
    + return 0;
    +}
    +EXPORT_SYMBOL(blk_integrity_register);
    +
    +/**
    + * blk_integrity_unregister - Remove block integrity profile
    + * @disk: disk whose integrity profile to deallocate
    + *
    + * Description: This function frees all memory used by the block
    + * integrity profile. To be called at device teardown.
    + */
    +void blk_integrity_unregister(struct gendisk *disk)
    +{
    + struct blk_integrity *bi;
    +
    + if (!disk || !disk->integrity)
    + return;
    +
    + bi = disk->integrity;
    +
    + kobject_uevent(&bi->kobj, KOBJ_REMOVE);
    + kobject_del(&bi->kobj);
    + kobject_put(&disk->dev.kobj);
    +}
    +EXPORT_SYMBOL(blk_integrity_unregister);
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/blk-merge.c
    --- a/block/blk-merge.c Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/blk-merge.c Sat Jun 07 00:45:15 2008 -0400
    @@ -441,6 +441,9 @@
    || next->special)
    return 0;

    + if (blk_integrity_rq(req) != blk_integrity_rq(next))
    + return 0;
    +
    /*
    * If we are allowed to merge, then append bio list
    * from next to rq and release next. merge_requests_fn
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/blk.h
    --- a/block/blk.h Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/blk.h Sat Jun 07 00:45:15 2008 -0400
    @@ -51,4 +51,12 @@
    return q->nr_congestion_off;
    }

    +#if defined(CONFIG_BLK_DEV_INTEGRITY)
    +
    +#define rq_for_each_integrity_segment(bvl, _rq, _iter) \
    + __rq_for_each_bio(_iter.bio, _rq) \
    + bip_for_each_vec(bvl, _iter.bio->bi_integrity, _iter.i)
    +
    +#endif /* BLK_DEV_INTEGRITY */
    +
    #endif
    diff -r f2ae9d5bce4c -r 5be7c534c954 block/elevator.c
    --- a/block/elevator.c Sat Jun 07 00:45:15 2008 -0400
    +++ b/block/elevator.c Sat Jun 07 00:45:15 2008 -0400
    @@ -84,6 +84,12 @@
    * must be same device and not a special request
    */
    if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
    + return 0;
    +
    + /*
    + * only merge integrity protected bio into ditto rq
    + */
    + if (bio_integrity(bio) != blk_integrity_rq(rq))
    return 0;

    if (!elv_iosched_allow_merge(rq, bio))
    diff -r f2ae9d5bce4c -r 5be7c534c954 include/linux/blkdev.h
    --- a/include/linux/blkdev.h Sat Jun 07 00:45:15 2008 -0400
    +++ b/include/linux/blkdev.h Sat Jun 07 00:45:15 2008 -0400
    @@ -113,6 +113,7 @@
    __REQ_ALLOCED, /* request came from our alloc pool */
    __REQ_RW_META, /* metadata io request */
    __REQ_COPY_USER, /* contains copies of user pages */
    + __REQ_INTEGRITY, /* integrity metadata has been remapped */
    __REQ_NR_BITS, /* stops here */
    };

    @@ -135,6 +136,7 @@
    #define REQ_ALLOCED (1 << __REQ_ALLOCED)
    #define REQ_RW_META (1 << __REQ_RW_META)
    #define REQ_COPY_USER (1 << __REQ_COPY_USER)
    +#define REQ_INTEGRITY (1 << __REQ_INTEGRITY)

    #define BLK_MAX_CDB 16

    @@ -866,6 +868,101 @@
    MODULE_ALIAS("block-major-" __stringify(major) "-*")


    +#if defined(CONFIG_BLK_DEV_INTEGRITY)
    +
    +#define INTEGRITY_FLAG_READ 1 /* verify data integrity on read */
    +#define INTEGRITY_FLAG_WRITE 2 /* generate data integrity on write */
    +
    +struct blk_integrity_exchg {
    + void *prot_buf;
    + void *data_buf;
    + sector_t sector;
    + unsigned int data_size;
    + unsigned short sector_size;
    + const char *disk_name;
    +};
    +
    +typedef void (integrity_gen_fn) (struct blk_integrity_exchg *);
    +typedef int (integrity_vrfy_fn) (struct blk_integrity_exchg *);
    +typedef void (integrity_set_tag_fn) (void *, void *, unsigned int);
    +typedef void (integrity_get_tag_fn) (void *, void *, unsigned int);
    +
    +struct blk_integrity {
    + integrity_gen_fn *generate_fn;
    + integrity_vrfy_fn *verify_fn;
    + integrity_set_tag_fn *set_tag_fn;
    + integrity_get_tag_fn *get_tag_fn;
    +
    + unsigned short flags;
    + unsigned short tuple_size;
    + unsigned short sector_size;
    + unsigned short tag_size;
    +
    + const char *name;
    +
    + struct kobject kobj;
    +};
    +
    +extern int blk_integrity_register(struct gendisk *, struct blk_integrity *);
    +extern void blk_integrity_unregister(struct gendisk *);
    +extern int blk_integrity_compare(struct block_device *, struct block_device *);
    +extern int blk_rq_map_integrity_sg(struct request *, struct scatterlist *);
    +extern int blk_rq_count_integrity_sg(struct request *);
    +
    +static inline unsigned short blk_integrity_tuple_size(struct blk_integrity *bi)
    +{
    + return (bi == NULL) ? 0 : bi->tuple_size;
    +}
    +
    +static inline struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
    +{
    + return bdev->bd_disk->integrity;
    +}
    +
    +static inline unsigned int bdev_get_tag_size(struct block_device *bdev)
    +{
    + struct blk_integrity *bi = bdev_get_integrity(bdev);
    +
    + return (bi == NULL) ? 0 : bi->tag_size;
    +}
    +
    +static inline int bdev_integrity_enabled(struct block_device *bdev, int rw)
    +{
    + struct blk_integrity *bi = bdev_get_integrity(bdev);
    +
    + if (bi == NULL)
    + return 0;
    +
    + if (rw == READ && bi->verify_fn != NULL &&
    + test_bit(INTEGRITY_FLAG_READ, &bi->flags))
    + return 1;
    +
    + if (rw == WRITE && bi->generate_fn != NULL &&
    + test_bit(INTEGRITY_FLAG_WRITE, &bi->flags))
    + return 1;
    +
    + return 0;
    +}
    +
    +static inline int blk_integrity_rq(struct request *rq)
    +{
    + BUG_ON(rq->bio == NULL);
    +
    + return bio_integrity(rq->bio);
    +}
    +
    +#else /* CONFIG_BLK_DEV_INTEGRITY */
    +
    +#define blk_integrity_rq(rq) (0)
    +#define bdev_get_integrity(a) (0)
    +#define bdev_get_tag_size(a) (0)
    +#define blk_integrity_compare(a, b) (0)
    +#define blk_integrity_register(a, b) (0)
    +#define blk_integrity_unregister(a) do { } while (0);
    +
    +#endif /* CONFIG_BLK_DEV_INTEGRITY */
    +
    +
    #else /* CONFIG_BLOCK */
    /*
    * stubs for when the block layer is configured out
    diff -r f2ae9d5bce4c -r 5be7c534c954 include/linux/genhd.h
    --- a/include/linux/genhd.h Sat Jun 07 00:45:15 2008 -0400
    +++ b/include/linux/genhd.h Sat Jun 07 00:45:15 2008 -0400
    @@ -141,6 +141,9 @@
    struct disk_stats dkstats;
    #endif
    struct work_struct async_notify;
    +#ifdef CONFIG_BLK_DEV_INTEGRITY
    + struct blk_integrity *integrity;
    +#endif
    };

    /*



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