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Linux 5.15 compat: block device readahead #12532

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merged 1 commit into from
Sep 8, 2021

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behlendorf
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Motivation and Context

Resolve the build failures caused by the 5.15 kernel release cycle starting.

http://build.zfsonlinux.org/builders/Kernel.org%20Built-in%20x86_64%20%28BUILD%29/builds/42957

Description

The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existence of either
the blk_queue_update_readahead() or disk_update_readahead()
functions. In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels. While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior. Removing it would
effectively increase the default readahead to 128k.

How Has This Been Tested?

Compiled against the v5.14-6779-g477f70cd2a67 kernel.

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Performance enhancement (non-breaking change which improves efficiency)
  • Code cleanup (non-breaking change which makes code smaller or more readable)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
  • Documentation (a change to man pages or other documentation)

Checklist:

The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
@behlendorf behlendorf added Type: Building Indicates an issue related to building binaries Status: Code Review Needed Ready for review and testing labels Sep 2, 2021
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@solbjorn solbjorn left a comment

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Looks nice, thanks!

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@tonynguien tonynguien left a comment

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Looks good. Nice to see builds completed successfully. Thanks!

@tonynguien tonynguien self-assigned this Sep 2, 2021
@behlendorf
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@ckane would you mind taking a look at this.

@behlendorf behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Sep 7, 2021
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ckane commented Sep 8, 2021

I was able to make this build earlier, but didn't get to test it myself, and now there's a more recent change in Linux that breaks compatibility w/ something else. This looks good to me.

@tonynguien tonynguien merged commit f616605 into openzfs:master Sep 8, 2021
@satmandu satmandu mentioned this pull request Sep 13, 2021
13 tasks
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Sep 15, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#12532
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Sep 16, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#12532
tonyhutter pushed a commit that referenced this pull request Sep 21, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #12532
rincebrain pushed a commit to rincebrain/zfs that referenced this pull request Sep 22, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#12532
tonyhutter pushed a commit that referenced this pull request Sep 22, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #12532
ghost pushed a commit to truenas/zfs that referenced this pull request Oct 7, 2021
The 5.15 kernel moved the backing_dev_info structure out of
the request queue structure which causes a build failure.

Rather than look in the new location for the BDI we instead
detect this upstream refactoring by the existance of either
the blk_queue_update_readahead() or disk_update_readahead()
functions.  In either case, there's no longer any reason to
manually set the ra_pages value since it will be overridden
with a reasonable default (2x the block size) when
blk_queue_io_opt() is called.

Therefore, we update the compatibility wrapper to do nothing
for 5.9 and newer kernels.  While it's tempting to do the
same for older kernels we want to keep the compatibility
code to preserve the existing behavior.  Removing it would
effectively increase the default readahead to 128k.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#12532
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4 participants