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Use specialFileFD handles in specialFileFD.Stat().

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PiperOrigin-RevId: 393831108
This commit is contained in:
Jamie Liu
2021-08-30 12:40:08 -07:00
committed by gVisor bot
parent 9625071e6d
commit 574c6542a5
1 changed files with 35 additions and 25 deletions
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pkg/sentry/fsimpl/gofer/gofer.go
+35 -25
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@@ -995,7 +995,7 @@ func (d *dentry) refreshSizeLocked(ctx context.Context) error {
if d.writeFD < 0 {
d.handleMu.RUnlock()
// Ask the gofer if we don't have a host FD.
return d.updateFromGetattrLocked(ctx)
return d.updateFromGetattrLocked(ctx, p9file{})
}
var stat unix.Statx_t
@@ -1014,33 +1014,35 @@ func (d *dentry) updateFromGetattr(ctx context.Context) error {
// updating stale attributes in d.updateFromP9AttrsLocked().
d.metadataMu.Lock()
defer d.metadataMu.Unlock()
return d.updateFromGetattrLocked(ctx)
return d.updateFromGetattrLocked(ctx, p9file{})
}
// Preconditions:
// * !d.isSynthetic().
// * d.metadataMu is locked.
// +checklocks:d.metadataMu
func (d *dentry) updateFromGetattrLocked(ctx context.Context) error {
// Use d.readFile or d.writeFile, which represent 9P FIDs that have been
// opened, in preference to d.file, which represents a 9P fid that has not.
// This may be significantly more efficient in some implementations. Prefer
// d.writeFile over d.readFile since some filesystem implementations may
// update a writable handle's metadata after writes to that handle, without
// making metadata updates immediately visible to read-only handles
// representing the same file.
d.handleMu.RLock()
handleMuRLocked := true
var file p9file
switch {
case !d.writeFile.isNil():
file = d.writeFile
case !d.readFile.isNil():
file = d.readFile
default:
file = d.file
d.handleMu.RUnlock()
handleMuRLocked = false
func (d *dentry) updateFromGetattrLocked(ctx context.Context, file p9file) error {
handleMuRLocked := false
if file.isNil() {
// Use d.readFile or d.writeFile, which represent 9P FIDs that have
// been opened, in preference to d.file, which represents a 9P fid that
// has not. This may be significantly more efficient in some
// implementations. Prefer d.writeFile over d.readFile since some
// filesystem implementations may update a writable handle's metadata
// after writes to that handle, without making metadata updates
// immediately visible to read-only handles representing the same file.
d.handleMu.RLock()
switch {
case !d.writeFile.isNil():
file = d.writeFile
handleMuRLocked = true
case !d.readFile.isNil():
file = d.readFile
handleMuRLocked = true
default:
file = d.file
d.handleMu.RUnlock()
}
}
_, attrMask, attr, err := file.getAttr(ctx, dentryAttrMask())
@@ -2044,9 +2046,17 @@ func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linu
d := fd.dentry()
const validMask = uint32(linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME | linux.STATX_SIZE | linux.STATX_BLOCKS | linux.STATX_BTIME)
if !d.cachedMetadataAuthoritative() && opts.Mask&validMask != 0 && opts.Sync != linux.AT_STATX_DONT_SYNC {
// TODO(jamieliu): Use specialFileFD.handle.file for the getattr if
// available?
if err := d.updateFromGetattr(ctx); err != nil {
// Use specialFileFD.handle.file for the getattr if available, for the
// same reason that we try to use open file handles in
// dentry.updateFromGetattrLocked().
var file p9file
if sffd, ok := fd.vfsfd.Impl().(*specialFileFD); ok {
file = sffd.handle.file
}
d.metadataMu.Lock()
err := d.updateFromGetattrLocked(ctx, file)
d.metadataMu.Unlock()
if err != nil {
return linux.Statx{}, err
}
}