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chunked: Add helpers for /proc/self/fd accesses 

It's not hard to grep for /proc/self/fd, but this way is a bit
cleaner and avoids typos, etc.

Signed-off-by: Colin Walters <walters@verbum.org>
This commit is contained in:
Colin Walters 2024-06-07 09:28:36 -04:00
parent 3ab2a4bbc0
commit cfde71b024
2 changed files with 20 additions and 7 deletions
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23
pkg/chunked/filesystem_linux.go
View File

@ -20,6 +20,19 @@ import (
"golang.org/x/sys/unix" "golang.org/x/sys/unix"
) )
// procPathForFile returns an absolute path in /proc which
// refers to the file; see procPathForFd.
func procPathForFile(f *os.File) string {
return procPathForFd(int(f.Fd()))
}
// procPathForFd returns an absolute path in /proc which
// refers to the file; this allows passing a file descriptor
// in places that don't accept a file descriptor.
func procPathForFd(fd int) string {
return fmt.Sprintf("/proc/self/fd/%d", fd)
}
// fileMetadata is a wrapper around internal.FileMetadata with additional private fields that // fileMetadata is a wrapper around internal.FileMetadata with additional private fields that
// are not part of the TOC document. // are not part of the TOC document.
// Type: TypeChunk entries are stored in Chunks, the primary [fileMetadata] entries never use TypeChunk. // Type: TypeChunk entries are stored in Chunks, the primary [fileMetadata] entries never use TypeChunk.
@ -39,7 +52,7 @@ func doHardLink(srcFd int, destDirFd int, destBase string) error {
doLink := func() error { doLink := func() error {
// Using unix.AT_EMPTY_PATH requires CAP_DAC_READ_SEARCH while this variant that uses // Using unix.AT_EMPTY_PATH requires CAP_DAC_READ_SEARCH while this variant that uses
// /proc/self/fd doesn't and can be used with rootless. // /proc/self/fd doesn't and can be used with rootless.
srcPath := fmt.Sprintf("/proc/self/fd/%d", srcFd) srcPath := procPathForFd(srcFd)
return unix.Linkat(unix.AT_FDCWD, srcPath, destDirFd, destBase, unix.AT_SYMLINK_FOLLOW) return unix.Linkat(unix.AT_FDCWD, srcPath, destDirFd, destBase, unix.AT_SYMLINK_FOLLOW)
} }
@ -55,7 +68,7 @@ func doHardLink(srcFd int, destDirFd int, destBase string) error {
func copyFileContent(srcFd int, fileMetadata *fileMetadata, dirfd int, mode os.FileMode, useHardLinks bool) (*os.File, int64, error) { func copyFileContent(srcFd int, fileMetadata *fileMetadata, dirfd int, mode os.FileMode, useHardLinks bool) (*os.File, int64, error) {
destFile := fileMetadata.Name destFile := fileMetadata.Name
src := fmt.Sprintf("/proc/self/fd/%d", srcFd) src := procPathForFd(srcFd)
st, err := os.Stat(src) st, err := os.Stat(src)
if err != nil { if err != nil {
return nil, -1, fmt.Errorf("copy file content for %q: %w", destFile, err) return nil, -1, fmt.Errorf("copy file content for %q: %w", destFile, err)
@ -153,7 +166,7 @@ func setFileAttrs(dirfd int, file *os.File, mode os.FileMode, metadata *fileMeta
if usePath { if usePath {
return unix.UtimesNanoAt(dirfd, baseName, ts, unix.AT_SYMLINK_NOFOLLOW) return unix.UtimesNanoAt(dirfd, baseName, ts, unix.AT_SYMLINK_NOFOLLOW)
} }
return unix.UtimesNanoAt(unix.AT_FDCWD, fmt.Sprintf("/proc/self/fd/%d", fd), ts, 0) return unix.UtimesNanoAt(unix.AT_FDCWD, procPathForFd(fd), ts, 0)
} }
doChmod := func() error { doChmod := func() error {
@ -197,7 +210,7 @@ func setFileAttrs(dirfd int, file *os.File, mode os.FileMode, metadata *fileMeta
} }
func openFileUnderRootFallback(dirfd int, name string, flags uint64, mode os.FileMode) (int, error) { func openFileUnderRootFallback(dirfd int, name string, flags uint64, mode os.FileMode) (int, error) {
root := fmt.Sprintf("/proc/self/fd/%d", dirfd) root := procPathForFd(dirfd)
targetRoot, err := os.Readlink(root) targetRoot, err := os.Readlink(root)
if err != nil { if err != nil {
@ -240,7 +253,7 @@ func openFileUnderRootFallback(dirfd int, name string, flags uint64, mode os.Fil
} }
} }
target, err := os.Readlink(fmt.Sprintf("/proc/self/fd/%d", fd)) target, err := os.Readlink(procPathForFd(fd))
if err != nil { if err != nil {
unix.Close(fd) unix.Close(fd)
return -1, err return -1, err

4
pkg/chunked/storage_linux.go
View File

@ -307,7 +307,7 @@ func canDedupFileWithHardLink(file *fileMetadata, fd int, s os.FileInfo) bool {
return false return false
} }
path := fmt.Sprintf("/proc/self/fd/%d", fd) path := procPathForFd(fd)
listXattrs, err := system.Llistxattr(path) listXattrs, err := system.Llistxattr(path)
if err != nil { if err != nil {
@ -987,7 +987,7 @@ type findAndCopyFileOptions struct {
} }
func reopenFileReadOnly(f *os.File) (*os.File, error) { func reopenFileReadOnly(f *os.File) (*os.File, error) {
path := fmt.Sprintf("/proc/self/fd/%d", f.Fd()) path := procPathForFile(f)
fd, err := unix.Open(path, unix.O_RDONLY|unix.O_CLOEXEC, 0) fd, err := unix.Open(path, unix.O_RDONLY|unix.O_CLOEXEC, 0)
if err != nil { if err != nil {
return nil, err return nil, err