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package fileutils
import (
"context"
"fmt"
"io"
"os"
"github.com/containerd/containerd/tracing"
"github.com/containerd/log"
"golang.org/x/sys/unix"
)
// GetTotalUsedFds Returns the number of used File Descriptors by
// reading it via /proc filesystem.
//
// Deprecated: this function is only used internally, and will be removed in the next release.
func GetTotalUsedFds(ctx context.Context) int {
ctx, span := tracing.StartSpan(ctx, "GetTotalUsedFds")
defer span.End()
name := fmt.Sprintf("/proc/%d/fd", os.Getpid())
// Fast-path for Linux 6.2 (since [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]).
// From the [Linux docs]:
//
// "The number of open files for the process is stored in 'size' member of
// stat() output for /proc/<pid>/fd for fast access."
//
// [Linux docs]: https://docs.kernel.org/filesystems/proc.html#proc-pid-fd-list-of-symlinks-to-open-files:
// [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]: https://github.com/torvalds/linux/commit/f1f1f2569901ec5b9d425f2e91c09a0e320768f3
var stat unix.Stat_t
if err := unix.Stat(name, &stat); err == nil && stat.Size > 0 {
return int(stat.Size)
}
f, err := os.Open(name)
if err != nil {
log.G(ctx).WithError(err).Error("Error listing file descriptors")
return -1
}
defer f.Close()
var fdCount int
for {
select {
case <-ctx.Done():
log.G(ctx).WithError(ctx.Err()).Error("Context cancelled while counting file descriptors")
return -1
default:
}
names, err := f.Readdirnames(100)
fdCount += len(names)
if err == io.EOF {
break
} else if err != nil {
log.G(ctx).WithError(err).Error("Error listing file descriptors")
return -1
}
}
// Note that the slow path has 1 more file-descriptor, due to the open
// file-handle for /proc/<pid>/fd during the calculation.
return fdCount
}
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