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zfs/config/kernel-bio-failfast.m4

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Add FAILFAST support ZFS works best when it is notified as soon as possible when a device failure occurs. This allows it to immediately start any recovery actions which may be needed. In theory Linux supports a flag which can be set on bio's called FAILFAST which provides this quick notification by disabling the retry logic in the lower scsi layers. That's the theory at least. In practice is turns out that while the flag exists you oddly have to set it with the BIO_RW_AHEAD flag. And even when it's set it you may get retries in the low level drivers decides that's the right behavior, or if you don't get the right error codes reported to the scsi midlayer. Unfortunately, without additional kernels patchs there's not much which can be done to improve this. Basically, this just means that it may take 2-3 minutes before a ZFS is notified properly that a device has failed. This can be improved and I suspect I'll be submitting patches upstream to handle this.
2010-10-01 17:57:56 +00:00
dnl #
Linux 2.6.36 compat, use REQ_FAILFAST_MASK As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags have been unified under the REQ_* names. These flags always had to be kept in-sync so this is a nice step forward, unfortunately it means we need to be careful to only use the new unified flags when the BIO_RW_* flags are not defined. Additional autoconf checks were added for this and if it is ever unclear which method to use no flags are set. This is safe but may result in longer delays before a disk is failed. Perferred interface for setting FAILFAST on a bio: 2.6.12-2.6.27: BIO_RW_FAILFAST 2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER} 2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
2010-11-10 22:40:38 +00:00
dnl # Preferred interface for setting FAILFAST on a bio:
dnl # 2.6.12-2.6.27: BIO_RW_FAILFAST
dnl # 2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER}
dnl # 2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
Add FAILFAST support ZFS works best when it is notified as soon as possible when a device failure occurs. This allows it to immediately start any recovery actions which may be needed. In theory Linux supports a flag which can be set on bio's called FAILFAST which provides this quick notification by disabling the retry logic in the lower scsi layers. That's the theory at least. In practice is turns out that while the flag exists you oddly have to set it with the BIO_RW_AHEAD flag. And even when it's set it you may get retries in the low level drivers decides that's the right behavior, or if you don't get the right error codes reported to the scsi midlayer. Unfortunately, without additional kernels patchs there's not much which can be done to improve this. Basically, this just means that it may take 2-3 minutes before a ZFS is notified properly that a device has failed. This can be improved and I suspect I'll be submitting patches upstream to handle this.
2010-10-01 17:57:56 +00:00
dnl #
AC_DEFUN([ZFS_AC_KERNEL_BIO_FAILFAST], [
Linux 2.6.36 compat, use REQ_FAILFAST_MASK As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags have been unified under the REQ_* names. These flags always had to be kept in-sync so this is a nice step forward, unfortunately it means we need to be careful to only use the new unified flags when the BIO_RW_* flags are not defined. Additional autoconf checks were added for this and if it is ever unclear which method to use no flags are set. This is safe but may result in longer delays before a disk is failed. Perferred interface for setting FAILFAST on a bio: 2.6.12-2.6.27: BIO_RW_FAILFAST 2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER} 2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
2010-11-10 22:40:38 +00:00
AC_MSG_CHECKING([whether BIO_RW_FAILFAST is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags;
flags = (1 << BIO_RW_FAILFAST);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BIO_RW_FAILFAST, 1,
[BIO_RW_FAILFAST is defined])
],[
AC_MSG_RESULT(no)
])
])
AC_DEFUN([ZFS_AC_KERNEL_BIO_FAILFAST_DTD], [
Add FAILFAST support ZFS works best when it is notified as soon as possible when a device failure occurs. This allows it to immediately start any recovery actions which may be needed. In theory Linux supports a flag which can be set on bio's called FAILFAST which provides this quick notification by disabling the retry logic in the lower scsi layers. That's the theory at least. In practice is turns out that while the flag exists you oddly have to set it with the BIO_RW_AHEAD flag. And even when it's set it you may get retries in the low level drivers decides that's the right behavior, or if you don't get the right error codes reported to the scsi midlayer. Unfortunately, without additional kernels patchs there's not much which can be done to improve this. Basically, this just means that it may take 2-3 minutes before a ZFS is notified properly that a device has failed. This can be improved and I suspect I'll be submitting patches upstream to handle this.
2010-10-01 17:57:56 +00:00
AC_MSG_CHECKING([whether BIO_RW_FAILFAST_* are defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags;
flags = ((1 << BIO_RW_FAILFAST_DEV) |
(1 << BIO_RW_FAILFAST_TRANSPORT) |
(1 << BIO_RW_FAILFAST_DRIVER));
],[
AC_MSG_RESULT(yes)
Linux 2.6.36 compat, use REQ_FAILFAST_MASK As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags have been unified under the REQ_* names. These flags always had to be kept in-sync so this is a nice step forward, unfortunately it means we need to be careful to only use the new unified flags when the BIO_RW_* flags are not defined. Additional autoconf checks were added for this and if it is ever unclear which method to use no flags are set. This is safe but may result in longer delays before a disk is failed. Perferred interface for setting FAILFAST on a bio: 2.6.12-2.6.27: BIO_RW_FAILFAST 2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER} 2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
2010-11-10 22:40:38 +00:00
AC_DEFINE(HAVE_BIO_RW_FAILFAST_DTD, 1,
Add FAILFAST support ZFS works best when it is notified as soon as possible when a device failure occurs. This allows it to immediately start any recovery actions which may be needed. In theory Linux supports a flag which can be set on bio's called FAILFAST which provides this quick notification by disabling the retry logic in the lower scsi layers. That's the theory at least. In practice is turns out that while the flag exists you oddly have to set it with the BIO_RW_AHEAD flag. And even when it's set it you may get retries in the low level drivers decides that's the right behavior, or if you don't get the right error codes reported to the scsi midlayer. Unfortunately, without additional kernels patchs there's not much which can be done to improve this. Basically, this just means that it may take 2-3 minutes before a ZFS is notified properly that a device has failed. This can be improved and I suspect I'll be submitting patches upstream to handle this.
2010-10-01 17:57:56 +00:00
[BIO_RW_FAILFAST_* are defined])
],[
AC_MSG_RESULT(no)
])
])
Linux 2.6.36 compat, use REQ_FAILFAST_MASK As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags have been unified under the REQ_* names. These flags always had to be kept in-sync so this is a nice step forward, unfortunately it means we need to be careful to only use the new unified flags when the BIO_RW_* flags are not defined. Additional autoconf checks were added for this and if it is ever unclear which method to use no flags are set. This is safe but may result in longer delays before a disk is failed. Perferred interface for setting FAILFAST on a bio: 2.6.12-2.6.27: BIO_RW_FAILFAST 2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER} 2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
2010-11-10 22:40:38 +00:00
AC_DEFUN([ZFS_AC_KERNEL_REQ_FAILFAST_MASK], [
AC_MSG_CHECKING([whether REQ_FAILFAST_MASK is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags;
flags = REQ_FAILFAST_MASK;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BIO_REQ_FAILFAST_MASK, 1,
[REQ_FAILFAST_MASK is defined])
],[
AC_MSG_RESULT(no)
])
])