[PATCH v3 4/9] loop:refactor: extract subfunction set_loop_info()

[Xiaoming Ni]

Step 4 of micro-refactoring the set_loop():
	Extract subfunction set_loop_info() from set_loop()

function                                             old     new   delta
set_loop                                             734     700     -34
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-34)             Total: -34 bytes

Signed-off-by: Xiaoming Ni <nixiaoming at huawei.com>
---
 libbb/loop.c | 91 +++++++++++++++++++++++++++-------------------------
 1 file changed, 47 insertions(+), 44 deletions(-)

diff --git a/libbb/loop.c b/libbb/loop.c
index 147597ab9..34e2dce7a 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -126,6 +126,47 @@ static int open_file(const char *file, unsigned flags, int *mode)
 	return ffd;
 }
 
+static int set_loop_info(int ffd, int lfd, const char *file,
+		unsigned long long offset, unsigned long long sizelimit, unsigned flags)
+{
+	int rc;
+	bb_loop_info loopinfo;
+
+	rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
+
+	/* If device is free, try to claim it */
+	if (rc && errno == ENXIO) {
+		/* Associate free loop device with file */
+		if (ioctl(lfd, LOOP_SET_FD, ffd)) {
+			return -1;
+		}
+		memset(&loopinfo, 0, sizeof(loopinfo));
+		safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
+		loopinfo.lo_offset = offset;
+		loopinfo.lo_sizelimit = sizelimit;
+		/*
+		 * Used by mount to set LO_FLAGS_AUTOCLEAR.
+		 * LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
+		 * Note that closing LO_FLAGS_AUTOCLEARed lfd before mount
+		 * is wrong (would free the loop device!)
+		 */
+		loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
+		rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
+		if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
+			/* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
+			/* (this code path is not tested) */
+			loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
+			rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
+		}
+		if (rc == 0) {
+			return lfd;
+		}
+		/* failure, undo LOOP_SET_FD */
+		ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+	}
+	return -1;
+}
+
 /* Returns opened fd to the loop device, <0 on error.
  * *device is loop device to use, or if *device==NULL finds a loop device to
  * mount it on and sets *device to a strdup of that loop device name.
@@ -135,7 +176,6 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 {
 	char dev[LOOP_NAMESIZE];
 	char *try;
-	bb_loop_info loopinfo;
 	struct stat statbuf;
 	int i, lfd, ffd, mode, rc;
 
@@ -190,49 +230,12 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 			}
 			goto try_next_loopN;
 		}
-
-		rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
-
-		/* If device is free, try to claim it */
-		if (rc && errno == ENXIO) {
-			/* Associate free loop device with file */
-			if (ioctl(lfd, LOOP_SET_FD, ffd)) {
-				close(lfd);
-				/* Ouch. Are we racing with other mount? */
-				if (!*device) {
-//TODO: add "if (--failcount != 0) ..."?
-					continue;
-				} else {
-					break;
-				}
-			}
-			memset(&loopinfo, 0, sizeof(loopinfo));
-			safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
-			loopinfo.lo_offset = offset;
-			loopinfo.lo_sizelimit = sizelimit;
-			/*
-			 * Used by mount to set LO_FLAGS_AUTOCLEAR.
-			 * LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
-			 * Note that closing LO_FLAGS_AUTOCLEARed lfd before mount
-			 * is wrong (would free the loop device!)
-			 */
-			loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
-			rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
-			if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
-				/* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
-				/* (this code path is not tested) */
-				loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
-				rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
-			}
-			if (rc == 0) {
-				/* SUCCESS! */
-				if (!*device)   /* was looping in search of free "/dev/loopN"? */
-					*device = xstrdup(dev);
-				rc = lfd; /* return this */
-				break;
-			}
-			/* failure, undo LOOP_SET_FD */
-			ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+		rc = set_loop_info(ffd, lfd, file, offset, sizelimit, flags);
+		if (rc == lfd) {
+			/* SUCCESS! */
+			if (!*device)
+				*device = xstrdup(dev);
+			break;
 		}
 		close(lfd);
  try_next_loopN:
-- 
2.27.0