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[release-branch.go1.20] Revert "internal/poll: drop redundant ENOSYS in CopyFileRange" 

This reverts CL 428555.

Reason for revert: It appears that even a newer kernel can get
ENOSYS from copy_file_range.

For #58592
Fixes #58627

Change-Id: Ib8dd1be61544f54bf652a99dc0b449109f8f50ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/470316
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Ian Lance Taylor 2023-02-21 23:00:01 +00:00 committed by Ian Lance Taylor
parent 7b398b1ff7
commit 1acd39cc92
1 changed files with 14 additions and 10 deletions
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24
src/internal/poll/copy_file_range_linux.go
View File

@ -41,18 +41,22 @@ func CopyFileRange(dst, src *FD, remain int64) (written int64, handled bool, err
}
n, err := copyFileRange(dst, src, int(max))
switch err {
case syscall.ENOSYS:
// copy_file_range(2) was introduced in Linux 4.5.
// Go supports Linux >= 2.6.33, so the system call
// may not be present.
//
// If we see ENOSYS, we have certainly not transferred
// any data, so we can tell the caller that we
// couldn't handle the transfer and let them fall
// back to more generic code.
return 0, false, nil
case syscall.EXDEV, syscall.EINVAL, syscall.EIO, syscall.EOPNOTSUPP, syscall.EPERM:
// Prior to Linux 5.3, it was not possible to
// copy_file_range across file systems. An attempt
// to do this will result in a EXDEV error.
//
// Even though we have checked the kernel version and blocked
// the attempts to copy_file_range(2) when the kernel version
// is older than 5.3, but until now the latest kernel (5.19.x)
// may still return EXDEV error in certain cases.
//
// If we see EXDEV, we have not transferred any data,
// and we can let the caller fall back to generic code.
// copy_file_range across file systems. Similarly to
// the ENOSYS case above, if we see EXDEV, we have
// not transferred any data, and we can let the caller
// fall back to generic code.
//
// As for EINVAL, that is what we see if, for example,
// dst or src refer to a pipe rather than a regular