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Reintroduce IO accounting on zvols on Linux 3.19+
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openzfs/zfs@e20cd6f caused us to
lose IO accounting on zvols. When I originally wrote that last year, the
symbols we needed to maintain IO accounting were GPL exported, but
torvalds/linux@394ffa5 provided
suitable symbols for restoring this functionality 4 months later.  We
can call them to restore the IO accounting on Linux 3.19 and later as
well as any older kernels where that patch is backported.

Closes openzfs#3741

Signed-off-by: Richard Yao <ryao@gentoo.org>
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ryao committed Sep 7, 2015
1 parent 3b36f83 commit 3d51dff
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Showing 4 changed files with 35 additions and 1 deletion.
24 changes: 24 additions & 0 deletions config/kernel-generic_io_acct.m4
Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
dnl #
dnl # 3.17 API addition
dnl #
dnl # torvalds/linux@394ffa503bc40e32d7f54a9b817264e81ce131b4 allows us to
dnl # increment iostat counters without generic_make_request().
dnl #
AC_DEFUN([ZFS_AC_KERNEL_GENERIC_IO_ACCT], [
AC_MSG_CHECKING([for generic IO accounting functions])
ZFS_LINUX_TRY_COMPILE_SYMBOL([
#include <linux/bio.h>
void (*generic_start_io_acct_f)(int, unsigned long,
struct hd_struct *) = &generic_start_io_acct;
void (*generic_end_io_acct_f)(int, unsigned long,
struct hd_struct *) = &generic_end_io_acct;
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_GENERIC_IO_ACCT, 1,
[generic_start_io_acct()/generic_end_io_acct() exist])
],[
AC_MSG_RESULT(no)
])
])
1 change: 1 addition & 0 deletions config/kernel.m4
Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_KMAP_ATOMIC_ARGS
ZFS_AC_KERNEL_FOLLOW_DOWN_ONE
ZFS_AC_KERNEL_MAKE_REQUEST_FN
ZFS_AC_KERNEL_GENERIC_IO_ACCT
AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"
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5 changes: 5 additions & 0 deletions include/linux/blkdev_compat.h
Original file line number Diff line number Diff line change
Expand Up @@ -343,4 +343,9 @@ blk_queue_discard_granularity(struct request_queue *q, unsigned int dg)
*/
#define VDEV_HOLDER ((void *)0x2401de7)

#ifndef HAVE_GENERIC_IO_ACCT
#define generic_start_io_acct(rw, slen, part)
#define generic_end_io_acct(rw, slen, part)
#endif

#endif /* _ZFS_BLKDEV_H */
6 changes: 5 additions & 1 deletion module/zfs/zvol.c
Original file line number Diff line number Diff line change
Expand Up @@ -713,6 +713,7 @@ zvol_request(struct request_queue *q, struct bio *bio)
fstrans_cookie_t cookie = spl_fstrans_mark();
uint64_t offset = BIO_BI_SECTOR(bio);
unsigned int sectors = bio_sectors(bio);
int rw = bio_data_dir(bio);
int error = 0;

if (bio_has_data(bio) && offset + sectors >
Expand All @@ -726,7 +727,9 @@ zvol_request(struct request_queue *q, struct bio *bio)
goto out;
}

if (bio_data_dir(bio) == WRITE) {
generic_start_io_acct(rw, sectors, zv->zv_disk->part0);

if (rw == WRITE) {
if (unlikely(zv->zv_flags & ZVOL_RDONLY)) {
error = SET_ERROR(EROFS);
goto out;
Expand All @@ -742,6 +745,7 @@ zvol_request(struct request_queue *q, struct bio *bio)
error = zvol_read(bio);

out:
generic_end_io_acct(rw, sectors, zv->zv_disk->part0);
bio_endio(bio, -error);
spl_fstrans_unmark(cookie);
#ifdef HAVE_MAKE_REQUEST_FN_RET_INT
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