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package mount
import (
"context"
"syscall"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/seaweedfs/seaweedfs/weed/filer"
"github.com/seaweedfs/seaweedfs/weed/glog"
)
// These are non-POSIX extensions
const (
SEEK_DATA uint32 = 3 // seek to next data after the offset
SEEK_HOLE uint32 = 4 // seek to next hole after the offset
ENXIO = fuse.Status(syscall.ENXIO)
)
// Lseek finds next data or hole segments after the specified offset
// See https://man7.org/linux/man-pages/man2/lseek.2.html
func (wfs *WFS) Lseek(cancel <-chan struct{}, in *fuse.LseekIn, out *fuse.LseekOut) fuse.Status {
// not a documented feature
if in.Padding != 0 {
return fuse.EINVAL
}
if in.Whence != SEEK_DATA && in.Whence != SEEK_HOLE {
return fuse.EINVAL
}
// file must exist
fh := wfs.GetHandle(FileHandleId(in.Fh))
if fh == nil {
return fuse.EBADF
}
// lock the file until the proper offset was calculated
fh.orderedMutex.Acquire(context.Background(), 1)
defer fh.orderedMutex.Release(1)
fh.entryLock.Lock()
defer fh.entryLock.Unlock()
fileSize := int64(filer.FileSize(fh.GetEntry()))
offset := max(int64(in.Offset), 0)
glog.V(4).Infof(
"Lseek %s fh %d in [%d,%d], whence %d",
fh.FullPath(), fh.fh, offset, fileSize, in.Whence,
)
// can neither seek beyond file nor seek to a hole at the end of the file with SEEK_DATA
if offset > fileSize {
return ENXIO
} else if in.Whence == SEEK_DATA && offset == fileSize {
return ENXIO
}
// refresh view cache if necessary
if fh.entryViewCache == nil {
var err error
fh.entryViewCache, err = filer.NonOverlappingVisibleIntervals(fh.wfs.LookupFn(), fh.entry.GetChunks(), 0, fileSize)
if err != nil {
return fuse.EIO
}
}
// search chunks for the offset
found, offset := searchChunks(fh, offset, fileSize, in.Whence)
if found {
out.Offset = uint64(offset)
return fuse.OK
}
// in case we found no exact matches, we return the recommended fallbacks, that is:
// original offset for SEEK_DATA or end of file for an implicit hole
if in.Whence == SEEK_DATA {
out.Offset = in.Offset
} else {
out.Offset = uint64(fileSize)
}
return fuse.OK
}
// searchChunks goes through all chunks to find the correct offset
func searchChunks(fh *FileHandle, offset, fileSize int64, whence uint32) (found bool, out int64) {
chunkViews := filer.ViewFromVisibleIntervals(fh.entryViewCache, offset, fileSize)
for _, chunkView := range chunkViews {
if offset < chunkView.LogicOffset {
if whence == SEEK_HOLE {
out = offset
} else {
out = chunkView.LogicOffset
}
return true, out
}
if offset >= chunkView.LogicOffset && offset < chunkView.Offset+int64(chunkView.Size) && whence == SEEK_DATA {
out = offset
return true, out
}
offset += int64(chunkView.Size)
}
return
}
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