mirror of
https://github.com/containers/podman.git
synced 2025-06-20 09:03:43 +08:00
f5b7bdac0c
Lots of fixes for issues found by podman. overlay: propagate errors from mountProgram utils: root in a userns uses global conf file Fix handling of additional stores Correctly check permissions on rootless directory Fix possible integer overflow on 32bit builds Evaluate device path for lvm lockfile test: make concurrent RW test determinisitc lockfile test: make concurrent read tests deterministic Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>
98 lines
3.0 KiB
Go
98 lines
3.0 KiB
Go
package storage
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import (
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"path/filepath"
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"sync"
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"time"
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"github.com/pkg/errors"
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)
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// A Locker represents a file lock where the file is used to cache an
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// identifier of the last party that made changes to whatever's being protected
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// by the lock.
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type Locker interface {
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// Acquire a writer lock.
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Lock()
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// Unlock the lock.
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Unlock()
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// Acquire a reader lock.
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RLock()
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// Touch records, for others sharing the lock, that the caller was the
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// last writer. It should only be called with the lock held.
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Touch() error
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// Modified() checks if the most recent writer was a party other than the
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// last recorded writer. It should only be called with the lock held.
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Modified() (bool, error)
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// TouchedSince() checks if the most recent writer modified the file (likely using Touch()) after the specified time.
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TouchedSince(when time.Time) bool
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// IsReadWrite() checks if the lock file is read-write
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IsReadWrite() bool
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// Locked() checks if lock is locked for writing by a thread in this process
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Locked() bool
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}
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var (
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lockfiles map[string]Locker
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lockfilesLock sync.Mutex
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)
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// GetLockfile opens a read-write lock file, creating it if necessary. The
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// Locker object may already be locked if the path has already been requested
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// by the current process.
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func GetLockfile(path string) (Locker, error) {
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return getLockfile(path, false)
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}
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// GetROLockfile opens a read-only lock file, creating it if necessary. The
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// Locker object may already be locked if the path has already been requested
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// by the current process.
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func GetROLockfile(path string) (Locker, error) {
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return getLockfile(path, true)
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}
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// getLockfile returns a Locker object, possibly (depending on the platform)
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// working inter-process, and associated with the specified path.
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//
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// If ro, the lock is a read-write lock and the returned Locker should correspond to the
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// “lock for reading” (shared) operation; otherwise, the lock is either an exclusive lock,
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// or a read-write lock and Locker should correspond to the “lock for writing” (exclusive) operation.
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//
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// WARNING:
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// - The lock may or MAY NOT be inter-process.
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// - There may or MAY NOT be an actual object on the filesystem created for the specified path.
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// - Even if ro, the lock MAY be exclusive.
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func getLockfile(path string, ro bool) (Locker, error) {
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lockfilesLock.Lock()
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defer lockfilesLock.Unlock()
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if lockfiles == nil {
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lockfiles = make(map[string]Locker)
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}
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cleanPath, err := filepath.Abs(path)
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if err != nil {
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return nil, errors.Wrapf(err, "error ensuring that path %q is an absolute path", path)
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}
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if locker, ok := lockfiles[cleanPath]; ok {
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if ro && locker.IsReadWrite() {
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return nil, errors.Errorf("lock %q is not a read-only lock", cleanPath)
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}
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if !ro && !locker.IsReadWrite() {
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return nil, errors.Errorf("lock %q is not a read-write lock", cleanPath)
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}
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return locker, nil
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}
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locker, err := createLockerForPath(path, ro) // platform-dependent locker
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if err != nil {
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return nil, err
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}
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lockfiles[filepath.Clean(path)] = locker
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return locker, nil
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}
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