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Cygwin: fcntl.h: Define O_TMPFILE and implement it

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Difference to Linux: We can't create files which don't show up
in the filesystem due to OS restrictions.  As a kludge, make a
(half-hearted) attempt to hide the file in the filesystem.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
2017-11-14 21:28:45 +01:00
parent f94fe74aad
commit 0aa99373c1
4 changed files with 103 additions and 3 deletions
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21
winsup/cygwin/fhandler.cc
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@@ -137,6 +137,11 @@ fhandler_base::set_name (path_conv &in_pc)
char *fhandler_base::get_proc_fd_name (char *buf)
{
/* If the file had been opened with O_TMPFILE | O_EXCL, don't
expose the filename. linkat is supposed to return ENOENT in this
case. See man 2 open on Linux. */
if ((get_flags () & (O_TMPFILE | O_EXCL)) == (O_TMPFILE | O_EXCL))
return strcpy (buf, "");
if (get_name ())
return strcpy (buf, get_name ());
if (dev ().name ())
@@ -582,7 +587,7 @@ fhandler_base::open (int flags, mode_t mode)
/* Don't use the FILE_OVERWRITE{_IF} flags here. See below for an
explanation, why that's not such a good idea. */
if ((flags & O_EXCL) && (flags & O_CREAT))
if (((flags & O_EXCL) && (flags & O_CREAT)) || (flags & O_TMPFILE))
create_disposition = FILE_CREATE;
else
create_disposition = (flags & O_CREAT) ? FILE_OPEN_IF : FILE_OPEN;
@@ -594,6 +599,18 @@ fhandler_base::open (int flags, mode_t mode)
if (pc.is_rep_symlink ())
options |= FILE_OPEN_REPARSE_POINT;
/* O_TMPFILE files are created with delete-on-close semantics, as well
as with FILE_ATTRIBUTE_TEMPORARY. The latter speeds up file access,
because the OS tries to keep the file in memory as much as possible.
In conjunction with FILE_DELETE_ON_CLOSE, ideally the OS never has
to write to the disk at all. */
if (flags & O_TMPFILE)
{
access |= DELETE;
file_attributes |= FILE_ATTRIBUTE_TEMPORARY;
options |= FILE_DELETE_ON_CLOSE;
}
if (pc.fs_is_nfs ())
{
/* Make sure we can read EAs of files on an NFS share. Also make
@@ -617,7 +634,7 @@ fhandler_base::open (int flags, mode_t mode)
&& has_attribute (FILE_ATTRIBUTE_HIDDEN | FILE_ATTRIBUTE_SYSTEM))
file_attributes |= pc.file_attributes ();
if (flags & O_CREAT)
if (flags & (O_CREAT | O_TMPFILE))
{
file_attributes |= FILE_ATTRIBUTE_NORMAL;