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syscall, x/sys/unix: wrong order of arguments for SyncFileRange on linux/ppc64{,le} #27485

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tklauser opened this issue Sep 4, 2018 · 4 comments
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syscall, x/sys/unix: wrong order of arguments for SyncFileRange on linux/ppc64{,le} #27485

tklauser opened this issue Sep 4, 2018 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. OS-Linux

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tklauser commented Sep 4, 2018 •
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While investigating what was wrong with https://golang.org/cl/133015 (see #27475), I noticed that the order of the syscall arguments in the SyncFileRange implementation is wrong for ppc64 and ppc64le. They use the SYS_SYNC_FILE_RANGE2 syscall which is defined as:

https://github.com/torvalds/linux/blob/60c1f89241d49bacf71035470684a8d7b4bb46ea/fs/sync.c#L371-L375

while SYS_SYNC_FILE_RANGE used by all other GOARCHes is defined as:

https://github.com/torvalds/linux/blob/60c1f89241d49bacf71035470684a8d7b4bb46ea/fs/sync.c#L363-L367

Note the different position of the flags argument. This should be fixed by using appropriate wrappers on linux/ppc64{,le}.

/cc @bradfitz @ianlancetaylor
@tklauser tklauser added OS-Linux NeedsFix The path to resolution is known, but the work has not been done. labels Sep 4, 2018
@tklauser tklauser self-assigned this Sep 4, 2018
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tklauser commented Sep 4, 2018

Also see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=edd5cd4a9424f22b0fa08bef5e299d41befd5622 for the reasoning for there being two syscalls.

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tklauser commented Sep 4, 2018

The implementation on linux/arm64 is correct, SYS_SYNC_FILE_RANGE and SYS_SYNC_FILE_RANGE2 have the same value and call the sync_file_range syscall.

@tklauser tklauser changed the title syscall, x/sys/unix: wrong order of arguments for SyncFileRange on linux/ppc64{,le} and arm64 syscall, x/sys/unix: wrong order of arguments for SyncFileRange on linux/ppc64{,le} Sep 4, 2018
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Change https://golang.org/cl/133195 mentions this issue: syscall: correct argument order for SyncFileRange syscall on linux/ppc64{,le

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Change https://golang.org/cl/133215 mentions this issue: unix: correct argument order for SyncFileRange syscall on linux/ppc64{,le}

gopherbot pushed a commit that referenced this issue Sep 5, 2018
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syscall: correct argument order for SyncFileRange syscall on linux/pp…

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eee1cfb 
…c64{,le}

On linux/ppc64{,le} the SYS_SYNC_FILE_RANGE2 syscall is used to
implement SyncFileRange. This syscall has a different argument order
than SYS_SYNC_FILE_RANGE. Apart from that the implementations of both
syscalls are the same, so use a simple wrapper to invoke the syscall
with the correct argument order.

For context see:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=edd5cd4a9424f22b0fa08bef5e299d41befd5622

Updates #27485

Change-Id: Ib94fb98376bf6c879df6f1b68c3bdd11ebcb5a44
Reviewed-on: https://go-review.googlesource.com/133195
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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