[PATCH RFC] xfs_io: simple bad buf hack to simulate write failure

[Brian Foster <bfoster@redhat.com>]

Hackily use a NULL buffer for the pwrite command to induce a kernel
write syscall failure. This is posted for reference only and needs a
proper implementation: needs a new flag, probably should be wired
through alloc_buffer(), etc.

Not-Signed-off-by: Brian Foster <bfoster@redhat.com>
---

Posted in prototype form in reference to the discussion here:

https://lore.kernel.org/linux-xfs/Y3e+7XH5gq5gc97u@bfoster/

Brian

 io/pwrite.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/io/pwrite.c b/io/pwrite.c
index 467bfa9f8..6e5de3140 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -285,12 +285,14 @@ pwrite_f(
 	int		direction = IO_FORWARD;
 	int		c, fd = -1;
 	int		pwritev2_flags = 0;
+	bool		fail = false;
+	char		*orig_io_buffer = NULL;
 
 	Cflag = qflag = uflag = dflag = wflag = Wflag = 0;
 	init_cvtnum(&fsblocksize, &fssectsize);
 	bsize = fsblocksize;
 
-	while ((c = getopt(argc, argv, "b:BCdDf:Fi:NqRs:OS:uV:wWZ:")) != EOF) {
+	while ((c = getopt(argc, argv, "b:BCdDfFi:NqRs:OS:uV:wWZ:")) != EOF) {
 		switch (c) {
 		case 'b':
 			tmp = cvtnum(fsblocksize, fssectsize, optarg);
@@ -320,6 +322,8 @@ pwrite_f(
 			dflag = 1;
 			break;
 		case 'f':
+			fail = true;
+			break;
 		case 'i':
 			infile = optarg;
 			break;
@@ -414,6 +418,10 @@ pwrite_f(
 		exitcode = 1;
 		return 0;
 	}
+	if (fail) {
+		orig_io_buffer = io_buffer;
+		io_buffer = NULL;
+	}
 
 	c = IO_READONLY | (dflag ? IO_DIRECT : 0);
 	if (infile && ((fd = openfile(infile, NULL, c, 0, NULL)) < 0)) {
@@ -471,6 +479,8 @@ pwrite_f(
 done:
 	if (infile)
 		close(fd);
+	if (orig_io_buffer)
+		io_buffer = orig_io_buffer;
 	return 0;
 }
 
-- 
2.37.3