linux: use O_EXCL when opening a file for write

On linux systems, opening a device with O_EXCL will fail with
EBUSY if the drive is in use.  For example, if a partition is
mounted on /dev/nvme1n1p1, the current mounted filesystem check
will allow running write workloads on /dev/nvme1n1 even if
allow_mounted_write is zero.  Opening /dev/nvme1n1 with O_EXCL
will fail with EBUSY in that case.  Add O_EXCL when opening a
file with O_WRONLY or O_RDWR on linux systems.

Fixes: #1820
Signed-of-by: Keith Reynolds <keith.reynolds@mext.ai>

engines/nvme.c

@@ -819,7 +819,14 @@ int fio_nvme_reset_wp(struct thread_data *td, struct fio_file *f,
 	/* If the file is not yet opened, open it for this function. */
 	fd = f->fd;
 	if (fd < 0) {
-		fd = open(f->file_name, O_RDWR | O_LARGEFILE);
+		int flags = O_RDWR | O_LARGEFILE;
+
+#ifdef FIO_USE_O_EXCL
+		if (!td->o.allow_mounted_write)
+			flags |= O_EXCL;
+#endif
+
+		fd = open(f->file_name, flags);
 		if (fd < 0)
 			return -errno;
 	}

engines/xnvme.c

@@ -302,6 +302,14 @@ static struct xnvme_opts xnvme_opts_from_fioe(struct thread_data *td)
 
 	opts.direct = td->o.odirect;
 
+	opts.rdonly = opts.wronly = opts.rdwr = 0;
+	if (td_rw(td))
+		opts.rdwr = 1;
+	else if (td_write(td))
+		opts.wronly = 1;
+	else
+		opts.rdonly = 1;
+
 	return opts;
 }
 

filesetup.c

@@ -719,6 +719,7 @@ int generic_open_file(struct thread_data *td, struct fio_file *f)
 	int is_std = 0;
 	int flags = 0;
 	int from_hash = 0;
+	int write_flags = O_RDWR;
 
 	dprint(FD_FILE, "fd open %s\n", f->file_name);
 
@@ -744,10 +745,15 @@ int generic_open_file(struct thread_data *td, struct fio_file *f)
 	if (f->filetype != FIO_TYPE_FILE)
 		flags |= FIO_O_NOATIME;
 
+#ifdef FIO_USE_O_EXCL
+	if (!td->o.allow_mounted_write && (flags & O_CREAT) == 0)
+		write_flags |= O_EXCL;
+#endif
+
 open_again:
 	if (td_write(td)) {
 		if (!read_only)
-			flags |= O_RDWR;
+			flags |= write_flags;
 
 		if (td->o.verify_only) {
 			flags &= ~O_RDWR;
@@ -763,7 +769,7 @@ int generic_open_file(struct thread_data *td, struct fio_file *f)
 			from_hash = file_lookup_open(f, flags);
 	} else if (td_read(td)) {
 		if (td_ioengine_flagged(td, FIO_RO_NEEDS_RW_OPEN) && !read_only)
-			flags |= O_RDWR;
+			flags |= write_flags;
 		else
 			flags |= O_RDONLY;
 
@@ -774,7 +780,7 @@ int generic_open_file(struct thread_data *td, struct fio_file *f)
 	} else if (td_trim(td)) {
 		assert(!td_rw(td)); /* should have matched above */
 		if (!read_only)
-			flags |= O_RDWR;
+			flags |= write_flags;
 		from_hash = file_lookup_open(f, flags);
 	}
 

os/os-linux.h

@@ -430,4 +430,6 @@ static inline bool os_cpu_has(cpu_features feature)
 	return have_feature;
 }
 
+#define FIO_USE_O_EXCL
+
 #endif

oslib/linux-blkzoned.c

@@ -323,7 +323,14 @@ int blkzoned_reset_wp(struct thread_data *td, struct fio_file *f,
 	/* If the file is not yet opened, open it for this function. */
 	fd = f->fd;
 	if (fd < 0) {
-		fd = open(f->file_name, O_RDWR | O_LARGEFILE);
+		int flags = O_RDWR | O_LARGEFILE;
+
+#ifdef FIO_USE_O_EXCL
+		if (!td->o.allow_mounted_write)
+			flags |= O_EXCL;
+#endif
+
+		fd = open(f->file_name, flags);
 		if (fd < 0)
 			return -errno;
 	}