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| author | Ian Lance Taylor <iant@golang.org> | 2021-02-14 17:14:41 -0800 |
|---|---|---|
| committer | Ian Lance Taylor <iant@golang.org> | 2021-02-16 00:46:04 +0000 |
| commit | 30641e36aa5b547eee48565caa3078b0a2e7c185 (patch) | |
| tree | c085c8c6f8f46883cc0877fcf400b4b910fb3e84 /src/internal | |
| parent | 33d72fd4122a4b7e31e738d5d9283093966ec14a (diff) | |
| download | go-30641e36aa5b547eee48565caa3078b0a2e7c185.tar.gz go-30641e36aa5b547eee48565caa3078b0a2e7c185.zip | |
internal/poll: if copy_file_range returns 0, assume it failed
On current Linux kernels copy_file_range does not correctly handle
files in certain special file systems, such as /proc. For those file
systems it fails to copy any data and returns zero. This breaks Go's
io.Copy for those files.
Fix the problem by assuming that if copy_file_range returns 0 the
first time it is called on a file, that that file is not supported.
In that case fall back to just using read. This will force an extra
system call when using io.Copy to copy a zero-sized normal file,
but at least it will work correctly.
For #36817
Fixes #44272
Change-Id: I02e81872cb70fda0ce5485e2ea712f219132e614
Reviewed-on: https://go-review.googlesource.com/c/go/+/291989
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Diffstat (limited to 'src/internal')
| -rw-r--r-- | src/internal/poll/copy_file_range_linux.go | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/src/internal/poll/copy_file_range_linux.go b/src/internal/poll/copy_file_range_linux.go index fc34aef4cb..01b242a4ea 100644 --- a/src/internal/poll/copy_file_range_linux.go +++ b/src/internal/poll/copy_file_range_linux.go @@ -112,7 +112,15 @@ func CopyFileRange(dst, src *FD, remain int64) (written int64, handled bool, err return 0, false, nil case nil: if n == 0 { - // src is at EOF, which means we are done. + // If we did not read any bytes at all, + // then this file may be in a file system + // where copy_file_range silently fails. + // https://lore.kernel.org/linux-fsdevel/20210126233840.GG4626@dread.disaster.area/T/#m05753578c7f7882f6e9ffe01f981bc223edef2b0 + if written == 0 { + return 0, false, nil + } + // Otherwise src is at EOF, which means + // we are done. return written, true, nil } remain -= n |