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Hello,
In recent kernels we are experiencing a problem that in our setup using SCST BLOCKIO backend some BIOs are finished, i.e. the finish callback called for them, with error -EIO. It happens quite often, much more often than one would expect to have an actual IO error. (BLOCKIO backend just converts all incoming SCSI commands to the corresponding block requests.)
After some investigation, we figured out, that, most likely, raid5.c::make_request() for some reason sometimes calls bio_endio() with not BIO_UPTODATE bios.
We bisected it to commit:
commit a82afdfcb8c0df09776b6458af6b68fc58b2e87b
Author: Tejun Heo <tj@kernel.org>
Date: Fri Jul 3 17:48:16 2009 +0900
block: use the same failfast bits for bio and request
bio and request use the same set of failfast bits. This patch makes
the following changes to simplify things.
* enumify BIO_RW* bits and reorder bits such that BIOS_RW_FAILFAST_*
bits coincide with __REQ_FAILFAST_* bits.
* The above pushes BIO_RW_AHEAD out of sync with __REQ_FAILFAST_DEV
but the matching is useless anyway. init_request_from_bio() is
responsible for setting FAILFAST bits on FS requests and non-FS
requests never use BIO_RW_AHEAD. Drop the code and comment from
blk_rq_bio_prep().
* Define REQ_FAILFAST_MASK which is OR of all FAILFAST bits and
simplify FAILFAST flags handling in init_request_from_bio().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
After looking at it I can't see how it can lead to the effect we are experiencing. Could anybody comment on this, please? Is it a known problem?
The error can be only reproduced when running RAID 5. The general layout is:
Disks --> RAID5 --> LVM --> BLOCKIO VDISK
The problem is easy to reproduce by forcing the RAID 5 array to re-sync its members, eg just fail out one member and add it back into the array and then generate some IO using dd. In fact, just ...Hello, That commit doesn't (or at least isn't supposed to) make any behavior difference. It's just repositioning flag bits. If the commit is actually causing the problem, I think one possibility is that whatever code could be using hard coded constants which now are mapped to different flags. The mixed merge changes have been in mainline for quite some time and shipping in all major distros too and this is the first time this is reported, so I don't think it could be a widespread problem. Thanks. -- tejun --
On Fri, 30 Jul 2010 12:29:30 +0200
The problem is that md/raid5 tests bio->bi_rw against RWA_MASK, which used to
align with BIO_RW_AHEAD, and now doesn't.
However the definition of bio_rw() in fs.h seems to justify that RWA_MASK
should align with BIO_RW_AHEAD, as does the definition of READA.
Given the current definitions, any WRITE request with BIO_RW_FAILFAST_DEV
set is going to confused a number of drives which test
bio_rw(bio) == WRITE
I guess RWA_MASK needs to be changed to (1<<BIO_RW_AHEAD), and READA need to
be change to that value too.
Can I leave that to you Tejun?
Thanks,
NeilBrown
--
Commit a82afdf (block: use the same failfast bits for bio and request) moved BIO_RW_* bits around such that they match up with REQ_* bits. Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1, 2 and 3, and expected them to match with BIO_RW_* bits. READ/WRITE didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1, breaking READA and SWRITE. This patch updates READA and SWRITE such that they match the BIO_RW_* bits again. A follow up patch will update the definitions to directly use BIO_RW_* bits so that this kind of breakage won't happen again. Stable: The offending commit a82afdf was released with v2.6.32, so this patch should be applied to all kernels since then but it must _NOT_ be applied to kernels earlier than that. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Vladislav Bolkhovitin <vst@vlnb.net> Root-caused-by: Neil Brown <neilb@suse.de> Cc: Jens Axobe <axboe@kernel.dk> Cc: stable@kernel.org --- Aieee... thanks for root causing it Neil. That was a stupid bug. I knew that READ/WRITE were hardcoded but forgot about READA. :-( Moving BIO_RW_AHEAD back to bit 1 might be a better solution but I'm afraid that would cause more confusions downstream. This patch updates READA and SWRITE to match BIO_RW_AHEAD and should also appear in -stable releases. The next patch will create bio_types.h and define all constants in terms of BIO_RW_*. Thanks. include/linux/fs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: work/include/linux/fs.h =================================================================== --- work.orig/include/linux/fs.h +++ work/include/linux/fs.h @@ -148,8 +148,8 @@ struct inodes_stat_t { #define RWA_MASK 2 #define READ 0 #define WRITE 1 -#define READA 2 /* read-ahead - don't block if no resources */ -#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */ +#define READA 16 /* read-ahead - don't block if no resources */ +#define SWRITE 17 /* for ...
linux/fs.h hard coded READ/WRITE constants which should match BIO_RW_*
flags. This is fragile and caused breakage during BIO_RW_* flag
rearrangement. The hardcoding is to avoid include dependency hell.
Create linux/bio_types.h which contatins definitions for bio data
structures and flags and include it from bio.h and fs.h, and make fs.h
define all READ/WRITE related constants in terms of BIO_RW_* flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axobe <axboe@kernel.dk>
---
include/linux/bio.h | 153 +-----------------------------------------
include/linux/bio_types.h | 164 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 17 ++--
3 files changed, 176 insertions(+), 158 deletions(-)
Index: work/include/linux/bio.h
===================================================================
--- work.orig/include/linux/bio.h
+++ work/include/linux/bio.h
@@ -9,7 +9,7 @@
*
* 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.
*
@@ -28,6 +28,9 @@
#include <asm/io.h>
+/* struct bio, bio_vec and BIO_* flags are defined in bio_types.h */
+#include <linux/bio_types.h>
+
#define BIO_DEBUG
#ifdef BIO_DEBUG
@@ -41,154 +44,6 @@
#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)
/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
- */
-struct bio_vec {
- struct page *bv_page;
- unsigned int bv_len;
- unsigned int bv_offset;
-};
-
-struct bio_set;
-struct bio;
-struct bio_integrity_payload;
-typedef void (bio_end_io_t) (struct bio *, int);
-typedef void (bio_destructor_t) (struct bio *);
-
-/*
- * main unit of I/O for the block layer and lower layers (ie drivers and
- * stacking drivers)
- */
-struct bio {
- sector_t bi_sector; /* device address in 512 byte
- sectors */
- struct ...linux/fs.h hard coded READ/WRITE constants which should match BIO_RW_*
flags. This is fragile and caused breakage during BIO_RW_* flag
rearrangement. The hardcoding is to avoid include dependency hell.
Create linux/bio_types.h which contatins definitions for bio data
structures and flags and include it from bio.h and fs.h, and make fs.h
define all READ/WRITE related constants in terms of BIO_RW_* flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axobe <axboe@kernel.dk>
---
include/linux/bio.h | 153 +-----------------------------------------
include/linux/bio_types.h | 164 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 17 ++--
3 files changed, 176 insertions(+), 158 deletions(-)
Index: work/include/linux/bio.h
===================================================================
--- work.orig/include/linux/bio.h
+++ work/include/linux/bio.h
@@ -9,7 +9,7 @@
*
* 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.
*
@@ -28,6 +28,9 @@
#include <asm/io.h>
+/* struct bio, bio_vec and BIO_* flags are defined in bio_types.h */
+#include <linux/bio_types.h>
+
#define BIO_DEBUG
#ifdef BIO_DEBUG
@@ -41,154 +44,6 @@
#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)
/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
- */
-struct bio_vec {
- struct page *bv_page;
- unsigned int bv_len;
- unsigned int bv_offset;
-};
-
-struct bio_set;
-struct bio;
-struct bio_integrity_payload;
-typedef void (bio_end_io_t) (struct bio *, int);
-typedef void (bio_destructor_t) (struct bio *);
-
-/*
- * main unit of I/O for the block layer and lower layers (ie drivers and
- * stacking drivers)
- */
-struct bio {
- sector_t bi_sector; /* device address in 512 byte
- sectors */
- struct ...linux/fs.h hard coded READ/WRITE constants which should match BIO_RW_*
flags. This is fragile and caused breakage during BIO_RW_* flag
rearrangement. The hardcoding is to avoid include dependency hell.
Create linux/bio_types.h which contatins definitions for bio data
structures and flags and include it from bio.h and fs.h, and make fs.h
define all READ/WRITE related constants in terms of BIO_RW_* flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axobe <axboe@kernel.dk>
---
include/linux/bio.h | 153 +-----------------------------------------
include/linux/bio_types.h | 164 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 17 ++--
3 files changed, 176 insertions(+), 158 deletions(-)
Index: work/include/linux/bio.h
===================================================================
--- work.orig/include/linux/bio.h
+++ work/include/linux/bio.h
@@ -9,7 +9,7 @@
*
* 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.
*
@@ -28,6 +28,9 @@
#include <asm/io.h>
+/* struct bio, bio_vec and BIO_* flags are defined in bio_types.h */
+#include <linux/bio_types.h>
+
#define BIO_DEBUG
#ifdef BIO_DEBUG
@@ -41,154 +44,6 @@
#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)
/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
- */
-struct bio_vec {
- struct page *bv_page;
- unsigned int bv_len;
- unsigned int bv_offset;
-};
-
-struct bio_set;
-struct bio;
-struct bio_integrity_payload;
-typedef void (bio_end_io_t) (struct bio *, int);
-typedef void (bio_destructor_t) (struct bio *);
-
-/*
- * main unit of I/O for the block layer and lower layers (ie drivers and
- * stacking drivers)
- */
-struct bio {
- sector_t bi_sector; /* device address in 512 byte
- sectors */
- struct ...Commit a82afdf (block: use the same failfast bits for bio and request) moved BIO_RW_* bits around such that they match up with REQ_* bits. Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1, 2 and 3, and expected them to match with BIO_RW_* bits. READ/WRITE didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1, breaking READA and SWRITE. This patch updates READA and SWRITE such that they match the BIO_RW_* bits again. A follow up patch will update the definitions to directly use BIO_RW_* bits so that this kind of breakage won't happen again. Stable: The offending commit a82afdf was released with v2.6.32, so this patch should be applied to all kernels since then but it must _NOT_ be applied to kernels earlier than that. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Vladislav Bolkhovitin <vst@vlnb.net> Root-caused-by: Neil Brown <neilb@suse.de> Cc: Jens Axobe <axboe@kernel.dk> Cc: stable@kernel.org --- Aieee... thanks for root causing it Neil. That was a stupid bug. I knew that READ/WRITE were hardcoded but forgot about READA. :-( Moving BIO_RW_AHEAD back to bit 1 might be a better solution but I'm afraid that would cause more confusions downstream. This patch updates READA and SWRITE to match BIO_RW_AHEAD and should also appear in -stable releases. The next patch will create bio_types.h and define all constants in terms of BIO_RW_*. Thanks. (resending w/ Jens' new address) include/linux/fs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: work/include/linux/fs.h =================================================================== --- work.orig/include/linux/fs.h +++ work/include/linux/fs.h @@ -148,8 +148,8 @@ struct inodes_stat_t { #define RWA_MASK 2 #define READ 0 #define WRITE 1 -#define READA 2 /* read-ahead - don't block if no resources */ -#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */ +#define READA 16 /* read-ahead - don't block if no resources ...
On Mon, 02 Aug 2010 16:15:38 +0200 Close, but not quite there - RWA_MASK must be 16 too !! Thanks, --
Would someone be so kind as to remind me how this problem manifests itself? I know I read this recently, but my memory and googling skills are both failing me. :( Cheers, Jeff --
See http://lkml.org/lkml/2010/7/28/315 and link inside. Vlad --
Hi Tejun, If only this patch goes into stable, do we need to change RWA_MASK in this patch also(I have seen you change it the 2/2)? -#define RWA_MASK 2 +#define RWA_MASK 16 Regards, Tao --
Hello, Yeah, Neil already pointed it out and updated patch has been posted and merged. Thanks. -- tejun --
I think RW_MASK and RWA_MASK should simply go away, they don't server any use over just masking the correct REQ_* flags. --
Commit a82afdf (block: use the same failfast bits for bio and request) moved BIO_RW_* bits around such that they match up with REQ_* bits. Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1, 2 and 3, and expected them to match with BIO_RW_* bits. READ/WRITE didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1, breaking READA and SWRITE. This patch updates READA and SWRITE such that they match the BIO_RW_* bits again. A follow up patch will update the definitions to directly use BIO_RW_* bits so that this kind of breakage won't happen again. Stable: The offending commit a82afdf was released with v2.6.32, so this patch should be applied to all kernels since then but it must _NOT_ be applied to kernels earlier than that. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Vladislav Bolkhovitin <vst@vlnb.net> Root-caused-by: Neil Brown <neilb@suse.de> Cc: Jens Axobe <axboe@kernel.dk> Cc: stable@kernel.org --- Aieee... thanks for root causing it Neil. That was a stupid bug. I knew that READ/WRITE were hardcoded but forgot about READA. :-( Moving BIO_RW_AHEAD back to bit 1 might be a better solution but I'm afraid that would cause more confusions downstream. This patch updates READA and SWRITE to match BIO_RW_AHEAD and should also appear in -stable releases. The next patch will create bio_types.h and define all constants in terms of BIO_RW_*. Thanks. (resending w/ Jens' new address) include/linux/fs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: work/include/linux/fs.h =================================================================== --- work.orig/include/linux/fs.h +++ work/include/linux/fs.h @@ -148,8 +148,8 @@ struct inodes_stat_t { #define RWA_MASK 2 #define READ 0 #define WRITE 1 -#define READA 2 /* read-ahead - don't block if no resources */ -#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */ +#define READA 16 /* read-ahead - don't block if no resources ...
Tejun, care to resend these against for-2.6.36? We can reference these for the stable backport (at least the first one should go in). -- Jens Axboe --
Commit a82afdf (block: use the same failfast bits for bio and request) moved BIO_RW_* bits around such that they match up with REQ_* bits. Unfortunately, fs.h hard coded RW_MASK, RWA_MASK, READ, WRITE, READA and SWRITE as 0, 1, 2 and 3, and expected them to match with BIO_RW_* bits. READ/WRITE didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1, breaking RWA_MASK, READA and SWRITE. This patch updates RWA_MASK, READA and SWRITE such that they match the BIO_RW_* bits again. A follow up patch will update the definitions to directly use BIO_RW_* bits so that this kind of breakage won't happen again. Neil also spotted missing RWA_MASK conversion. Stable: The offending commit a82afdf was released with v2.6.32, so this patch should be applied to all kernels since then but it must _NOT_ be applied to kernels earlier than that. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Vladislav Bolkhovitin <vst@vlnb.net> Root-caused-by: Neil Brown <neilb@suse.de> Cc: Jens Axobe <axboe@kernel.dk> Cc: stable@kernel.org --- Here's the regenerated version also w/ the missing RWA_MASK conversion Neil spotted. Thanks. include/linux/fs.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) Index: work/include/linux/fs.h =================================================================== --- work.orig/include/linux/fs.h +++ work/include/linux/fs.h @@ -145,12 +145,12 @@ struct inodes_stat_t { * */ #define RW_MASK 1 -#define RWA_MASK 2 +#define RWA_MASK 16 #define READ 0 #define WRITE 1 -#define READA 2 /* readahead - don't block if no resources */ -#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */ +#define READA 16 /* readahead - don't block if no resources */ +#define SWRITE 17 /* for ll_rw_block(), wait for buffer lock */ #define READ_SYNC (READ | REQ_SYNC | REQ_UNPLUG) #define READ_META (READ | REQ_META) --
^^^^^ (Too) common typo :-) Anyway, applied to for-2.6.36, thanks a lot. -- Jens Axboe --
Irk, we have an issue:
In file included from fs/coda/psdev.c:48:
include/linux/coda_psdev.h:91:1: warning: "REQ_WRITE" redefined
In file included from include/linux/fs.h:11,
from include/linux/proc_fs.h:5,
from fs/coda/psdev.c:31:
include/linux/blk_types.h:154:1: warning: this is the location of the previous definition
And from include/linux/coda_psdev.h:
#define REQ_ASYNC 0x1
#define REQ_READ 0x2
#define REQ_WRITE 0x4
#define REQ_ABORT 0x8
which unfortunately seem to not be under __KERNEL__ protection, but
there are things like wait_queue_head_t structs there as well so should
be safe to change.
--
Jens Axboe
Confidentiality Notice: This e-mail message, its contents and any attachments to it are confidential to the intended recipient, and may contain information that is privileged and/or exempt from disclosure under applicable law. If you are not the intended recipient, please immediately notify the sender and destroy the original e-mail message and any attachments (and any copies that may have been made) from your system or otherwise. Any unauthorized use, copying, disclosure or distribution of this information is strictly prohibited.
--
(cc'ing CODA people) Hello, Oops, I'm sorry. Heh, it reminds me of misspelling Linus's last name Yeah, I hate it when symbols in non-core code doesn't have proper prefix. Prefixing CODA_ in front of those macros should do it. Jan Harkes, would that work for CODA? Thanks. -- tejun --
REQ_* constants are used for block layer requests causing inconsistent
duplicate definitions of REQ_WRITE. Rename REQ_* used by coda to
CODA_REQ_*.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
So, something like this. Build tested only.
Thanks.
fs/coda/psdev.c | 14 +++++++-------
fs/coda/upcall.c | 12 ++++++------
include/linux/coda_psdev.h | 8 ++++----
3 files changed, 17 insertions(+), 17 deletions(-)
Index: work/fs/coda/psdev.c
===================================================================
--- work.orig/fs/coda/psdev.c
+++ work/fs/coda/psdev.c
@@ -177,7 +177,7 @@ static ssize_t coda_psdev_write(struct f
nbytes = req->uc_outSize; /* don't have more space! */
}
if (copy_from_user(req->uc_data, buf, nbytes)) {
- req->uc_flags |= REQ_ABORT;
+ req->uc_flags |= CODA_REQ_ABORT;
wake_up(&req->uc_sleep);
retval = -EFAULT;
goto out;
@@ -185,7 +185,7 @@ static ssize_t coda_psdev_write(struct f
/* adjust outsize. is this useful ?? */
req->uc_outSize = nbytes;
- req->uc_flags |= REQ_WRITE;
+ req->uc_flags |= CODA_REQ_WRITE;
count = nbytes;
/* Convert filedescriptor into a file handle */
@@ -254,8 +254,8 @@ static ssize_t coda_psdev_read(struct fi
retval = -EFAULT;
/* If request was not a signal, enqueue and don't free */
- if (!(req->uc_flags & REQ_ASYNC)) {
- req->uc_flags |= REQ_READ;
+ if (!(req->uc_flags & CODA_REQ_ASYNC)) {
+ req->uc_flags |= CODA_REQ_READ;
list_add_tail(&(req->uc_chain), &vcp->vc_processing);
goto out;
}
@@ -315,19 +315,19 @@ static int coda_psdev_release(struct ino
list_del(&req->uc_chain);
/* Async requests need to be freed here */
- if (req->uc_flags & REQ_ASYNC) {
+ if (req->uc_flags & CODA_REQ_ASYNC) {
CODA_FREE(req->uc_data, sizeof(struct coda_in_hdr));
kfree(req);
continue;
}
- req->uc_flags |= REQ_ABORT;
+ req->uc_flags |= CODA_REQ_ABORT;
wake_up(&req->uc_sleep);
}
...Looks good to me. Acked-by: Jan Harkes <jaharkes@cs.cmu.edu> --
Should have been clear, I committed the fixup already: http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=ceb1fde0d5c7611fdb9004176ac3414... Looks byte-for-byte identical :-) -- Jens Axboe Confidentiality Notice: This e-mail message, its contents and any attachments to it are confidential to the intended recipient, and may contain information that is privileged and/or exempt from disclosure under applicable law. If you are not the intended recipient, please immediately notify the sender and destroy the original e-mail message and any attachments (and any copies that may have been made) from your system or otherwise. Any unauthorized use, copying, disclosure or distribution of this information is strictly prohibited. --
linux/fs.h hard coded READ/WRITE constants which should match BIO_RW_*
flags. This is fragile and caused breakage during BIO_RW_* flag
rearrangement. The hardcoding is to avoid include dependency hell.
Create linux/bio_types.h which contatins definitions for bio data
structures and flags and include it from bio.h and fs.h, and make fs.h
define all READ/WRITE related constants in terms of BIO_RW_* flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axobe <axboe@kernel.dk>
---
I renamed the file to blk_types.h instead of bio_types.h as it now
contains the REQ bits too.
include/linux/bio.h | 183 -------------------------------------------
include/linux/blk_types.h | 193 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 15 +--
3 files changed, 204 insertions(+), 187 deletions(-)
Index: work/include/linux/bio.h
===================================================================
--- work.orig/include/linux/bio.h
+++ work/include/linux/bio.h
@@ -9,7 +9,7 @@
*
* 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.
*
@@ -28,6 +28,9 @@
#include <asm/io.h>
+/* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
+#include <linux/blk_types.h>
+
#define BIO_DEBUG
#ifdef BIO_DEBUG
@@ -41,184 +44,6 @@
#define BIO_MAX_SECTORS (BIO_MAX_SIZE >> 9)
/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
- */
-struct bio_vec {
- struct page *bv_page;
- unsigned int bv_len;
- unsigned int bv_offset;
-};
-
-struct bio_set;
-struct bio;
-struct bio_integrity_payload;
-typedef void (bio_end_io_t) (struct bio *, int);
-typedef void (bio_destructor_t) (struct bio *);
-
-/*
- * main unit of I/O for the block layer and lower layers (ie drivers and
- * stacking drivers)
- ...