From 7273058c66b82508c5935f8c59c382db225383ae Mon Sep 17 00:00:00 2001
From: Sitsofe Wheeler <sitsofe@yahoo.com>
Date: Sun, 1 Mar 2020 18:27:19 +0000
Subject: [PATCH] filesetup: fix win raw disk access and improve dir creation
 failure msg

The commit df18600fd06258b96ae6f6b530ecdff541c2a82d ("filesetup: fix
directory creation issues") broke Windows raw/physical disk access
because Windows doesn't consider a path that only consists of a
namespace (such as the device namespace "\\.\" - see
https://docs.microsoft.com/en-gb/windows/win32/fileio/naming-a-file?redirectedfrom=MSDN#namespaces
for information on Windows' namespaces) to exist as a directory(!).

Workaround the issue for raw devices by explicitly considering the
device namespace subcomponent to always be valid. Further, intermediate
path components in UNC paths or paths starting with a namespace might
also not "exist" so introduce backwards scanning for the longest
pre-existing directory to sidestep this. The function doing this is made
available for non-windows platforms so a similar code path is used
everywhere.

Tests done:

Windows:
> ./fio.exe --name=dtest --thread --size=16k --rw=write `
  --filename 'fio.tmp'
> ./fio.exe --name=dtest --thread --size=16k --rw=write `
  --filename '\\?\C\:\Windows\Temp\fio\fio.tmp'
> Clear-Disk 1 -RemoveData -Confirm:$false # Destroys partition data!
> ./fio.exe --name=dtest --thread --size=16k --rw=write `
   --filename '\\.\PhysicalDrive1'
> ./fio.exe --name=dtest --thread --size=16k --rw=write `
  --filename '\fio.tmp'
> ./fio.exe --name=dtest --thread --size=16k --rw=write `
  --filename '\\LOCALHOST\Users\User\fio\fio.tmp'

macOS:
$ rm -rf /tmp/fio
$ ./fio --name=dtest --size=16k --filename /tmp/fio/fio.tmp \
  --rw=write

Finally, change the directory creation error message to give a human
error message rather than just an errno.

Fixes: https://github.com/axboe/fio/issues/916
Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>
---
 filesetup.c     | 52 ++++++++++++++++++++++++++++++++++++++++++++++---
 os/os-windows.h |  6 +++++-
 2 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/filesetup.c b/filesetup.c
index b45a5826..8a4091fc 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -913,15 +913,61 @@ uint64_t get_start_offset(struct thread_data *td, struct fio_file *f)
 	return offset;
 }
 
+/*
+ * Find longest path component that exists and return its length
+ */
+int longest_existing_path(char *path) {
+	char buf[PATH_MAX];
+	bool done;
+	char *buf_pos;
+	int offset;
+#ifdef WIN32
+	DWORD dwAttr;
+#else
+	struct stat sb;
+#endif
+
+	sprintf(buf, "%s", path);
+	done = false;
+	while (!done) {
+		buf_pos = strrchr(buf, FIO_OS_PATH_SEPARATOR);
+		if (!buf_pos) {
+			done = true;
+			offset = 0;
+			break;
+		}
+
+		*(buf_pos + 1) = '\0';
+
+#ifdef WIN32
+		dwAttr = GetFileAttributesA(buf);
+		if (dwAttr != INVALID_FILE_ATTRIBUTES) {
+			done = true;
+		}
+#else
+		if (stat(buf, &sb) == 0)
+			done = true;
+#endif
+		if (done)
+			offset = buf_pos - buf;
+		else
+			*buf_pos = '\0';
+	}
+
+	return offset;
+}
+
 static bool create_work_dirs(struct thread_data *td, const char *fname)
 {
 	char path[PATH_MAX];
 	char *start, *end;
+	int offset;
 
 	snprintf(path, PATH_MAX, "%s", fname);
 	start = path;
 
-	end = start;
+	offset = longest_existing_path(path);
+	end = start + offset;
 	while ((end = strchr(end, FIO_OS_PATH_SEPARATOR)) != NULL) {
 		if (end == start) {
 			end++;
@@ -930,8 +976,8 @@ static bool create_work_dirs(struct thread_data *td, const char *fname)
 		*end = '\0';
 		errno = 0;
 		if (fio_mkdir(path, 0700) && errno != EEXIST) {
-			log_err("fio: failed to create dir (%s): %d\n",
-				start, errno);
+			log_err("fio: failed to create dir (%s): %s\n",
+				start, strerror(errno));
 			return false;
 		}
 		*end = FIO_OS_PATH_SEPARATOR;
diff --git a/os/os-windows.h b/os/os-windows.h
index 6d48ffe8..fa2955f9 100644
--- a/os/os-windows.h
+++ b/os/os-windows.h
@@ -203,7 +203,11 @@ static inline int fio_mkdir(const char *path, mode_t mode) {
 	}
 
 	if (CreateDirectoryA(path, NULL) == 0) {
-		log_err("CreateDirectoryA = %d\n", GetLastError());
+		/* Ignore errors if path is a device namespace */
+		if (strcmp(path, "\\\\.") == 0) {
+			errno = EEXIST;
+			return -1;
+		}
 		errno = win_to_posix_error(GetLastError());
 		return -1;
 	}
-- 
2.25.1