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-rw-r--r--pkg/sentry/fsimpl/gofer/regular_file.go41
-rw-r--r--pkg/sentry/fsimpl/gofer/special_file.go56
2 files changed, 81 insertions, 16 deletions
diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index f10350c97..02317a133 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -155,26 +155,53 @@ func (fd *regularFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts
// PWrite implements vfs.FileDescriptionImpl.PWrite.
func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+ n, _, err := fd.pwrite(ctx, src, offset, opts)
+ return n, err
+}
+
+// pwrite returns the number of bytes written, final offset, error. The final
+// offset should be ignored by PWrite.
+func (fd *regularFileFD) pwrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (written, finalOff int64, err error) {
if offset < 0 {
- return 0, syserror.EINVAL
+ return 0, offset, syserror.EINVAL
}
// Check that flags are supported.
//
// TODO(gvisor.dev/issue/2601): Support select pwritev2 flags.
if opts.Flags&^linux.RWF_HIPRI != 0 {
- return 0, syserror.EOPNOTSUPP
+ return 0, offset, syserror.EOPNOTSUPP
+ }
+
+ d := fd.dentry()
+ // If the fd was opened with O_APPEND, make sure the file size is updated.
+ // There is a possible race here if size is modified externally after
+ // metadata cache is updated.
+ if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 && !d.cachedMetadataAuthoritative() {
+ if err := d.updateFromGetattr(ctx); err != nil {
+ return 0, offset, err
+ }
}
+ d.metadataMu.Lock()
+ defer d.metadataMu.Unlock()
+ // Set offset to file size if the fd was opened with O_APPEND.
+ if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 {
+ // Holding d.metadataMu is sufficient for reading d.size.
+ offset = int64(d.size)
+ }
limit, err := vfs.CheckLimit(ctx, offset, src.NumBytes())
if err != nil {
- return 0, err
+ return 0, offset, err
}
src = src.TakeFirst64(limit)
+ n, err := fd.pwriteLocked(ctx, src, offset, opts)
+ return n, offset + n, err
+}
+// Preconditions: fd.dentry().metatdataMu must be locked.
+func (fd *regularFileFD) pwriteLocked(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
d := fd.dentry()
- d.metadataMu.Lock()
- defer d.metadataMu.Unlock()
if d.fs.opts.interop != InteropModeShared {
// Compare Linux's mm/filemap.c:__generic_file_write_iter() =>
// file_update_time(). This is d.touchCMtime(), but without locking
@@ -237,8 +264,8 @@ func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
// Write implements vfs.FileDescriptionImpl.Write.
func (fd *regularFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
fd.mu.Lock()
- n, err := fd.PWrite(ctx, src, fd.off, opts)
- fd.off += n
+ n, off, err := fd.pwrite(ctx, src, fd.off, opts)
+ fd.off = off
fd.mu.Unlock()
return n, err
}
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index a7b53b2d2..811528982 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -16,6 +16,7 @@ package gofer
import (
"sync"
+ "sync/atomic"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
@@ -144,7 +145,7 @@ func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
// mmap due to lock ordering; MM locks precede dentry.dataMu. That doesn't
// hold here since specialFileFD doesn't client-cache data. Just buffer the
// read instead.
- if d := fd.dentry(); d.fs.opts.interop != InteropModeShared {
+ if d := fd.dentry(); d.cachedMetadataAuthoritative() {
d.touchAtime(fd.vfsfd.Mount())
}
buf := make([]byte, dst.NumBytes())
@@ -176,39 +177,76 @@ func (fd *specialFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts
// PWrite implements vfs.FileDescriptionImpl.PWrite.
func (fd *specialFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+ n, _, err := fd.pwrite(ctx, src, offset, opts)
+ return n, err
+}
+
+// pwrite returns the number of bytes written, final offset, error. The final
+// offset should be ignored by PWrite.
+func (fd *specialFileFD) pwrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (written, finalOff int64, err error) {
if fd.seekable && offset < 0 {
- return 0, syserror.EINVAL
+ return 0, offset, syserror.EINVAL
}
// Check that flags are supported.
//
// TODO(gvisor.dev/issue/2601): Support select pwritev2 flags.
if opts.Flags&^linux.RWF_HIPRI != 0 {
- return 0, syserror.EOPNOTSUPP
+ return 0, offset, syserror.EOPNOTSUPP
+ }
+
+ d := fd.dentry()
+ // If the regular file fd was opened with O_APPEND, make sure the file size
+ // is updated. There is a possible race here if size is modified externally
+ // after metadata cache is updated.
+ if fd.seekable && fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 && !d.cachedMetadataAuthoritative() {
+ if err := d.updateFromGetattr(ctx); err != nil {
+ return 0, offset, err
+ }
}
if fd.seekable {
+ // We need to hold the metadataMu *while* writing to a regular file.
+ d.metadataMu.Lock()
+ defer d.metadataMu.Unlock()
+
+ // Set offset to file size if the regular file was opened with O_APPEND.
+ if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 {
+ // Holding d.metadataMu is sufficient for reading d.size.
+ offset = int64(d.size)
+ }
limit, err := vfs.CheckLimit(ctx, offset, src.NumBytes())
if err != nil {
- return 0, err
+ return 0, offset, err
}
src = src.TakeFirst64(limit)
}
// Do a buffered write. See rationale in PRead.
- if d := fd.dentry(); d.fs.opts.interop != InteropModeShared {
+ if d.cachedMetadataAuthoritative() {
d.touchCMtime()
}
buf := make([]byte, src.NumBytes())
// Don't do partial writes if we get a partial read from src.
if _, err := src.CopyIn(ctx, buf); err != nil {
- return 0, err
+ return 0, offset, err
}
n, err := fd.handle.writeFromBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
if err == syserror.EAGAIN {
err = syserror.ErrWouldBlock
}
- return int64(n), err
+ finalOff = offset
+ // Update file size for regular files.
+ if fd.seekable {
+ finalOff += int64(n)
+ // d.metadataMu is already locked at this point.
+ if uint64(finalOff) > d.size {
+ d.dataMu.Lock()
+ defer d.dataMu.Unlock()
+ atomic.StoreUint64(&d.size, uint64(finalOff))
+ }
+ }
+ return int64(n), finalOff, err
}
// Write implements vfs.FileDescriptionImpl.Write.
@@ -218,8 +256,8 @@ func (fd *specialFileFD) Write(ctx context.Context, src usermem.IOSequence, opts
}
fd.mu.Lock()
- n, err := fd.PWrite(ctx, src, fd.off, opts)
- fd.off += n
+ n, off, err := fd.pwrite(ctx, src, fd.off, opts)
+ fd.off = off
fd.mu.Unlock()
return n, err
}
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