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Cygwin: don't use unlink/rename POSIX semantics on certain NTFS 

If a host NTFS is mapped into a Hyper-V isolated container, the
OPEN_BY_FILE_ID filesystem flag is missing, just as if that NTFS
is a remote drive.  However, NtQueryVolumeInformationFile claims
the drive is a local drive.

We can use this fact to learn that the process is running under
Hyper-V, and that the Hyper-V isolated process can't use rename/unlink
with POSIX semantics.  Strange enough, the POSIX_UNLINK_RENAME filesystem
flag is still set...

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2023-03-21 18:29:59 +01:00
parent 0a962aa2c2
commit fe2545e9fa
1 changed files with 9 additions and 5 deletions
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14
winsup/cygwin/syscalls.cc
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@ -691,10 +691,12 @@ unlink_nt (path_conv &pc, bool shareable)
pc.get_object_attr (attr, sec_none_nih);
/* First check if we can use POSIX unlink semantics: W10 1709+, local NTFS.
With POSIX unlink semantics the entire job gets MUCH easier and faster.
Just try to do it and if it fails, it fails. */
For the OPEN_BY_FILE_ID flag, see MINIMAL_WIN_NTFS_FLAGS comment in
fs_info::update. With POSIX unlink semantics the entire job gets MUCH
easier and faster. Just try to do it and if it fails, it fails. */
if (wincap.has_posix_unlink_semantics ()
&& !pc.isremote () && pc.fs_is_ntfs ())
&& !pc.isremote () && pc.fs_is_ntfs ()
&& pc.has_attribute (FILE_SUPPORTS_OPEN_BY_FILE_ID))
{
FILE_DISPOSITION_INFORMATION_EX fdie;
@ -2407,10 +2409,12 @@ rename2 (const char *oldpath, const char *newpath, unsigned int at2flags)
__leave;
}
/* POSIX semantics only on local NTFS drives. */
/* POSIX semantics only on local NTFS drives. For the OPEN_BY_FILE_ID
flag, see MINIMAL_WIN_NTFS_FLAGS comment in fs_info::update. */
use_posix_semantics = wincap.has_posix_rename_semantics ()
&& !oldpc.isremote ()
&& oldpc.fs_is_ntfs ();
&& oldpc.fs_is_ntfs ()
&& oldpc.has_attribute (FILE_SUPPORTS_OPEN_BY_FILE_ID);
/* Opening the file must be part of the transaction. It's not sufficient
to call only NtSetInformationFile under the transaction. Therefore we