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>

diff --git a/lib/loopdev.c b/lib/loopdev.c
index d49738fde122220e0ab2c2e941ce712bfdb0ec81..d89c795ed2d8090331b19b7137f55849027fde65 100644 (file)
--- 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)
  */
@@ -1454,7 +1457,7 @@ 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);
@@ -1468,9 +1471,12 @@ 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"));
@@ -1524,16 +1530,24 @@ 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;