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lib/fs: an attempt to fix SIGBUS error by rounding mmap`ed region to multiple of 4KB pages

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Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/581
This commit is contained in:
Aliaksandr Valialkin 2020-06-23 13:39:12 +03:00
parent b5206ce33f
commit c970cb912c
1 changed files with 9 additions and 2 deletions
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11
lib/fs/reader_at.go
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@ -133,7 +133,7 @@ func (r *ReaderAt) MustClose() {
fname := r.f.Name()
if len(r.mmapData) > 0 {
if err := unix.Munmap(r.mmapData); err != nil {
if err := unix.Munmap(r.mmapData[:cap(r.mmapData)]); err != nil {
logger.Panicf("FATAL: cannot unmap data for file %q: %s", fname, err)
}
r.mmapData = nil
@ -214,9 +214,16 @@ func mmapFile(f *os.File, size int64) ([]byte, error) {
if int64(int(size)) != size {
return nil, fmt.Errorf("file is too big to be mmap'ed: %d bytes", size)
}
// Round size to multiple of 4KB pages as `man 2 mmap` recommends.
// This may help preventing SIGBUS panic at https://github.com/VictoriaMetrics/VictoriaMetrics/issues/581
// The SIGBUS could occur if standard copy(dst, src) function may read beyond src bounds.
sizeOrig := size
if size%4096 != 0 {
size += 4096 - size%4096
}
data, err := unix.Mmap(int(f.Fd()), 0, int(size), unix.PROT_READ, unix.MAP_SHARED)
if err != nil {
return nil, fmt.Errorf("cannot mmap file with size %d: %s", size, err)
}
return data, nil
return data[:sizeOrig], nil
}