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Cygwin: utilize FILE_DISPOSITION_POSIX_SEMANTICS 

- short-circuit most code in unlink_nt since it's not necessary
  anymore if FILE_DISPOSITION_POSIX_SEMANTICS is supported.

- Immediately remove O_TMPFILE from filesystem after creation.
  Disable code for now because we have to implement /proc/self/fd
  opening by handle first, lest linkat fails.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2018-12-23 21:36:42 +01:00
parent 0c25ca40ce
commit a7f392686b
1 changed files with 76 additions and 3 deletions
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79
winsup/cygwin/syscalls.cc
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@ -658,23 +658,64 @@ unlink_nt (path_conv &pc)
HANDLE fh, fh_ro = NULL;
OBJECT_ATTRIBUTES attr;
IO_STATUS_BLOCK io;
ACCESS_MASK access = DELETE;
ULONG flags = FILE_OPEN_FOR_BACKUP_INTENT;
HANDLE old_trans = NULL, trans = NULL;
ULONG num_links = 1;
FILE_DISPOSITION_INFORMATION disp = { TRUE };
int reopened = 0;
bin_status bin_stat = dont_move;
syscall_printf ("Trying to delete %S, isdir = %d",
pc.get_nt_native_path (), pc.isdir ());
ACCESS_MASK access = DELETE;
ULONG flags = FILE_OPEN_FOR_BACKUP_INTENT;
/* Add the reparse point flag to known reparse points, otherwise we remove
the target, not the reparse point. */
if (pc.is_known_reparse_point ())
flags |= FILE_OPEN_REPARSE_POINT;
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. */
if (wincap.has_posix_file_info () && !pc.isremote () && pc.fs_is_ntfs ())
{
FILE_DISPOSITION_INFORMATION_EX fdie;
if (pc.file_attributes () & FILE_ATTRIBUTE_READONLY)
access |= FILE_WRITE_ATTRIBUTES;
status = NtOpenFile (&fh, access, &attr, &io, FILE_SHARE_VALID_FLAGS,
flags);
if (!NT_SUCCESS (status))
goto out;
/* Why didn't the devs add a FILE_DELETE_IGNORE_READONLY_ATTRIBUTE
flag just like they did with FILE_LINK_IGNORE_READONLY_ATTRIBUTE
and FILE_LINK_IGNORE_READONLY_ATTRIBUTE???
POSIX unlink semantics are nice, but they still fail if the file
has the R/O attribute set. Removing the file is very much a safe
bet afterwards, so, no transaction. */
if (pc.file_attributes () & FILE_ATTRIBUTE_READONLY)
{
status = NtSetAttributesFile (fh, pc.file_attributes ()
& ~FILE_ATTRIBUTE_READONLY);
if (!NT_SUCCESS (status))
{
NtClose (fh);
goto out;
}
}
fdie.Flags = FILE_DISPOSITION_DELETE | FILE_DISPOSITION_POSIX_SEMANTICS;
status = NtSetInformationFile (fh, &io, &fdie, sizeof fdie,
FileDispositionInformationEx);
/* Restore R/O attribute in case we have multiple hardlinks. */
if (pc.file_attributes () & FILE_ATTRIBUTE_READONLY)
NtSetAttributesFile (fh, pc.file_attributes ());
NtClose (fh);
goto out;
}
/* If the R/O attribute is set, we have to open the file with
FILE_WRITE_ATTRIBUTES to be able to remove this flags before trying
to delete it. We do this separately because there are filesystems
@ -1426,7 +1467,39 @@ open (const char *unix_path, int flags, ...)
if ((fh->is_fs_special () && fh->device_access_denied (flags))
|| !fh->open_with_arch (flags, mode & 07777))
__leave; /* errno already set */
#if 0
/* W10 1709 POSIX unlink semantics:
TODO: Works nicely for O_TEMPFILE but using linkat requires that
we first fix /proc/self/fd handling to allow opening by handle
rather than by symlinked filename only. */
if ((flags & O_TMPFILE) && wincap.has_posix_file_info ()
&& fh->pc.fs_is_ntfs ())
{
HANDLE del_h;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
IO_STATUS_BLOCK io;
FILE_DISPOSITION_INFORMATION_EX fdie;
status = NtOpenFile (&del_h, DELETE,
fh->pc.init_reopen_attr (attr, fh->get_handle ()), &io,
FILE_SHARE_VALID_FLAGS, FILE_OPEN_FOR_BACKUP_INTENT);
if (!NT_SUCCESS (status))
debug_printf ("reopening tmpfile handle failed, status %y", status);
else
{
fdie.Flags = FILE_DISPOSITION_DELETE
| FILE_DISPOSITION_POSIX_SEMANTICS;
status = NtSetInformationFile (del_h, &io, &fdie, sizeof fdie,
FileDispositionInformationEx);
if (!NT_SUCCESS (status))
debug_printf ("Setting POSIX delete disposition on tmpfile "
"failed, status = %y", status);
NtClose (del_h);
}
}
#endif
fd = fh;
if (fd <= 2)
set_std_handle (fd);