[PATCH 06/12] uapi: deprecate STATX_ALL

From: Miklos Szeredi <mszeredi@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>
Subject: [PATCH 06/12] uapi: deprecate STATX_ALL
Date: Tue,  5 May 2020 11:59:09 +0200	[thread overview]
Message-ID: <20200505095915.11275-7-mszeredi@redhat.com> (raw)
In-Reply-To: <20200505095915.11275-1-mszeredi@redhat.com>

Constants of the *_ALL type can be actively harmful due to the fact that
developers will usually fail to consider the possible effects of future
changes to the definition.

Deprecate STATX_ALL in the uapi, while no damage has been done yet.

We could keep something like this around in the kernel, but there's
actually no point, since all filesystems should be explicitly checking
flags that they support and not rely on the VFS masking unknown ones out: a
flag could be known to the VFS, yet not known to the filesystem.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
---
 fs/stat.c                       |  1 -
 include/uapi/linux/stat.h       | 11 ++++++++++-
 samples/vfs/test-statx.c        |  2 +-
 tools/include/uapi/linux/stat.h | 11 ++++++++++-
 4 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/fs/stat.c b/fs/stat.c
index 030008796479..a6709e7ba71d 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -70,7 +70,6 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
 
 	memset(stat, 0, sizeof(*stat));
 	stat->result_mask |= STATX_BASIC_STATS;
-	request_mask &= STATX_ALL;
 	query_flags &= KSTAT_QUERY_FLAGS;
 
 	/* allow the fs to override these if it really wants to */
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index ad80a5c885d5..d1192783139a 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -148,9 +148,18 @@ struct statx {
 #define STATX_BLOCKS		0x00000400U	/* Want/got stx_blocks */
 #define STATX_BASIC_STATS	0x000007ffU	/* The stuff in the normal stat struct */
 #define STATX_BTIME		0x00000800U	/* Want/got stx_btime */
-#define STATX_ALL		0x00000fffU	/* All currently supported flags */
+
 #define STATX__RESERVED		0x80000000U	/* Reserved for future struct statx expansion */
 
+#ifndef __KERNEL__
+/*
+ * This is deprecated, and shall remain the same value in the future.  To avoid
+ * confusion please use the equivalent (STATX_BASIC_STATS | STATX_BTIME)
+ * instead.
+ */
+#define STATX_ALL		0x00000fffU
+#endif
+
 /*
  * Attributes to be found in stx_attributes and masked in stx_attributes_mask.
  *
diff --git a/samples/vfs/test-statx.c b/samples/vfs/test-statx.c
index a3d68159fb51..76c577ea4fd8 100644
--- a/samples/vfs/test-statx.c
+++ b/samples/vfs/test-statx.c
@@ -216,7 +216,7 @@ int main(int argc, char **argv)
 	struct statx stx;
 	int ret, raw = 0, atflag = AT_SYMLINK_NOFOLLOW;
 
-	unsigned int mask = STATX_ALL;
+	unsigned int mask = STATX_BASIC_STATS | STATX_BTIME;
 
 	for (argv++; *argv; argv++) {
 		if (strcmp(*argv, "-F") == 0) {
diff --git a/tools/include/uapi/linux/stat.h b/tools/include/uapi/linux/stat.h
index ad80a5c885d5..d1192783139a 100644
--- a/tools/include/uapi/linux/stat.h
+++ b/tools/include/uapi/linux/stat.h
@@ -148,9 +148,18 @@ struct statx {
 #define STATX_BLOCKS		0x00000400U	/* Want/got stx_blocks */
 #define STATX_BASIC_STATS	0x000007ffU	/* The stuff in the normal stat struct */
 #define STATX_BTIME		0x00000800U	/* Want/got stx_btime */
-#define STATX_ALL		0x00000fffU	/* All currently supported flags */
+
 #define STATX__RESERVED		0x80000000U	/* Reserved for future struct statx expansion */
 
+#ifndef __KERNEL__
+/*
+ * This is deprecated, and shall remain the same value in the future.  To avoid
+ * confusion please use the equivalent (STATX_BASIC_STATS | STATX_BTIME)
+ * instead.
+ */
+#define STATX_ALL		0x00000fffU
+#endif
+
 /*
  * Attributes to be found in stx_attributes and masked in stx_attributes_mask.
  *
-- 
2.21.1

