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[v2,1/2] aio-dio-eof-race: handle aio pwrite errors and short reads

Message ID d928f86c748db034ca4efd849e01c5c2bf805199.1523509644.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Omar Sandoval April 12, 2018, 5:07 a.m. UTC
From: Omar Sandoval <osandov@fb.com>

generic/427 fails on Btrfs with a cryptic "pread: Success" message. This
is because an aio pwrite fails with ENOSPC, so the file isn't as long as
we expect it to be. Make sure we check the result of the aio writes and
also print a more explicit message for short reads (which are
technically valid but in practice shouldn't happen for this test case).
Now the test fails with a much more informative "pwrite: No space left
on device".

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 src/aio-dio-regress/aio-dio-eof-race.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)
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Patch

diff --git a/src/aio-dio-regress/aio-dio-eof-race.c b/src/aio-dio-regress/aio-dio-eof-race.c
index bb1890b5..04479035 100644
--- a/src/aio-dio-regress/aio-dio-eof-race.c
+++ b/src/aio-dio-regress/aio-dio-eof-race.c
@@ -154,6 +154,9 @@  int main(int argc, char *argv[])
 
 	/* Keep extending until size_MB */
 	while (eof < size_MB * 1024 * 1024) {
+		ssize_t sret;
+		int i;
+
 		memset(buf, IO_PATTERN, buf_size);
 		fstat(fd, &statbuf);
 		eof = statbuf.st_size;
@@ -186,15 +189,32 @@  int main(int argc, char *argv[])
 			return 1;
 		}
 
+		for (i = 0; i < err; i++) {
+			/*
+			 * res is unsigned for some reason, so this is the best
+			 * way to detect that it contains a negative errno.
+			 */
+			if (evs[i].res > buf_size / 4) {
+				fprintf(stderr, "pwrite: %s\n",
+					strerror(-evs[i].res));
+				return 1;
+			}
+		}
+
 		/*
 		 * And then read it back.
 		 *
 		 * Using pread to keep it simple, but AIO has the same effect.
 		 * eof is the prior eof; we just wrote buf_size more.
 		 */
-		if (pread(fd, buf, buf_size, eof) != buf_size) {
+		sret = pread(fd, buf, buf_size, eof);
+		if (sret == -1) {
 			perror("pread");
 			return 1;
+		} else if (sret != buf_size) {
+			fprintf(stderr, "short read %zd was less than %zu\n",
+				sret, buf_size);
+			return 1;
 		}
 
 		/*