On Wed, Nov 20, 2019 at 08:57:32PM +0100, Florian Weimer wrote: > * Rich Felker: > > > An issue was reported today on the Alpine Linux tracker at > > https://gitlab.alpinelinux.org/alpine/aports/issues/10960 regarding > > readdir results from SMB/NFS shares with musl libc. > > > > After a good deal of analysis, we determined the root cause to be that > > the second and subsequent calls to getdents64 are dropping/skipping > > direntries (that have not yet been deleted) when some entries were > > deleted following the previous call. The issue appears to happen only > > when the buffer size passed to getdents64 is below some threshold > > greater than 2k (the size musl uses) but less than 32k (the size glibc > > uses, with which we were unable to reproduce the issue). > > >From the Gitlab issue: > > while ((dp = readdir(dir)) != NULL) { > unlink(dp->d_name); > ++file_cnt; > } > > I'm not sure that this is valid code to delete the contents of a > directory. It's true that POSIX says this: I think it is. > | If a file is removed from or added to the directory after the most > | recent call to opendir() or rewinddir(), whether a subsequent call > | to readdir() returns an entry for that file is unspecified. ^^^^^^^^^^^^^ POSIX only allows both behaviors (showing or not showing) the entry that was deleted. It does not allow deletion of one entry to cause other entries not to be seen. > But many file systems simply provide not the necessary on-disk data > structures which are need to ensure stable iteration in the face of > modification of the directory. There are hacks, of course, such as > compacting the on-disk directory only on file creation, which solves > the file removal case. > > For deleting an entire directory, that is not really a problem because > you can stick another loop around this while loop which re-reads the > directory after rewinddir. Eventually, it will become empty. This is still a serious problem and affects usage other than deletion of an entire directory. Rich
