From a24905f03e90fb2f418bd5b8816378a99bb535b2 Mon Sep 17 00:00:00 2001

From: Karel Zak <kzak@redhat.com>

Date: Tue, 1 Mar 2022 12:07:07 +0100

Subject: loopdev: add retries on EAGAIN

* add limit to number of attempts for LOOP_SET_STATUS64

* use the same for LOOP_SET_BLOCK_SIZE ioctl

Addresses: https://github.com/util-linux/util-linux/issues/1582

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 lib/loopdev.c | 32 +++++++++++++++++++++++---------

 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/lib/loopdev.c b/lib/loopdev.c

index 511f8a0d6..e8ccf6ae6 100644

--- a/lib/loopdev.c

+++ b/lib/loopdev.c

@@ -43,6 +43,9 @@

 #include "debug.h"

 #include "fileutils.h"

+

+#define LOOPDEV_MAX_TRIES	10

+

 /*

  * Debug stuff (based on include/debug.h)

  */

@@ -1450,7 +1453,7 @@ err:

  */

 int loopcxt_ioctl_status(struct loopdev_cxt *lc)

 {

-	int dev_fd, rc = -1, err, again;

+	int dev_fd, rc = -1, err, again, tries = 0;

 	errno = 0;

 	dev_fd = loopcxt_get_fd(lc);

@@ -1464,9 +1467,12 @@ int loopcxt_ioctl_status(struct loopdev_cxt *lc)

 	do {

 		err = ioctl(dev_fd, LOOP_SET_STATUS64, &lc->config.info);

 		again = err && errno == EAGAIN;

-		if (again)

+		if (again) {

 			xusleep(250000);

-	} while (again);

+			tries++;

+		}

+	} while (again && tries <= LOOPDEV_MAX_TRIES);

+

 	if (err) {

 		rc = -errno;

 		DBG(SETUP, ul_debugobj(lc, "LOOP_SET_STATUS64 failed: %m"));

@@ -1520,16 +1526,24 @@ int loopcxt_ioctl_dio(struct loopdev_cxt *lc, unsigned long use_dio)

 int loopcxt_ioctl_blocksize(struct loopdev_cxt *lc, uint64_t blocksize)

 {

 	int fd = loopcxt_get_fd(lc);

+	int err, again, tries = 0;

 	if (fd < 0)

 		return -EINVAL;

-	/* Kernels prior to v4.14 don't support this ioctl */

-	if (ioctl(fd, LOOP_SET_BLOCK_SIZE, (unsigned long) blocksize) < 0) {

-		int rc = -errno;

-		DBG(CXT, ul_debugobj(lc, "LOOP_SET_BLOCK_SIZE failed: %m"));

-		return rc;

-	}

+	do {

+		/* Kernels prior to v4.14 don't support this ioctl */

+		err = ioctl(fd, LOOP_SET_BLOCK_SIZE, (unsigned long) blocksize);

+		again = err && errno == EAGAIN;

+		if (again) {

+			xusleep(250000);

+			tries++;

+		} else if (err) {

+			int rc = -errno;

+			DBG(CXT, ul_debugobj(lc, "LOOP_SET_BLOCK_SIZE failed: %m"));

+			return rc;

+		}

+	} while (again && tries <= LOOPDEV_MAX_TRIES);

 	DBG(CXT, ul_debugobj(lc, "logical block size set"));

 	return 0;

-- 

2.37.1