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List:       busybox
Subject:    [PATCH v3 6/9] loop:refactor: Use a structure to reduce parameters
From:       Xiaoming Ni <nixiaoming () huawei ! com>
Date:       2022-11-21 2:46:36
Message-ID: 20221121024639.92549-7-nixiaoming () huawei ! com
[Download RAW message or body]

Step 6 of micro-refactoring the set_loop():
	Use structs to avoid transferring a large number of parameters
	in set_loop_configure() and set_loop_info()

function                                             old     new   delta
set_loop                                             708     720     +12
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 12/0)               Total: 12 bytes

Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
---
 libbb/loop.c | 54 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/libbb/loop.c b/libbb/loop.c
index dc8ecc9a8..0b1336a02 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -126,32 +126,21 @@ static int open_file(const char *file, unsigned flags, int *mode)
 	return ffd;
 }
 
-static int set_loop_configure(int ffd, int lfd, const char *file,
-		unsigned long long offset, unsigned long long sizelimit, unsigned flags)
+static int set_loop_configure(int ffd, int lfd, bb_loop_info *loopinfo)
 {
 	int rc;
-	bb_loop_info loopinfo;
+	bb_loop_info loopinfo2;
 	/* 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)) {
+	rc = ioctl(lfd, BB_LOOP_SET_STATUS, loopinfo);
+	if (rc != 0 && (loopinfo->lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
+		memcpy(&loopinfo2, loopinfo, sizeof(*loopinfo));
 		/* 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);
+		loopinfo2.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
+		rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo2);
 	}
 	if (rc == 0) {
 		return lfd;
@@ -161,21 +150,36 @@ static int set_loop_configure(int ffd, int lfd, const char *file,
 	return -1;
 }
 
-static int set_loop_info(int ffd, int lfd, const char *file,
-		unsigned long long offset, unsigned long long sizelimit, unsigned flags)
+static int set_loop_info(int ffd, int lfd, bb_loop_info *loopinfo)
 {
 	int rc;
-	bb_loop_info loopinfo;
+	bb_loop_info tmp;
 
-	rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
+	rc = ioctl(lfd, BB_LOOP_GET_STATUS, &tmp);
 
 	/* If device is free, try to claim it */
 	if (rc && errno == ENXIO) {
-		return set_loop_configure(ffd, lfd, file, offset, sizelimit, flags);
+		return set_loop_configure(ffd, lfd, loopinfo);
 	}
 	return -1;
 }
 
+static void init_bb_loop_info(bb_loop_info *loopinfo, const char *file,
+		unsigned long long offset, unsigned long long sizelimit, unsigned flags)
+{
+	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);
+}
+
 /* 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.
@@ -187,12 +191,14 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 	char *try;
 	struct stat statbuf;
 	int i, lfd, ffd, mode, rc;
+	bb_loop_info loopinfo;
 
 	ffd = open_file(file, flags, &mode);
 	if (ffd < 0) {
 		return -errno;
 	}
 
+	init_bb_loop_info(&loopinfo, file, offset, sizelimit, flags);
 	try = *device;
 	if (!try) {
 		try = dev;
@@ -239,7 +245,7 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 			}
 			goto try_next_loopN;
 		}
-		rc = set_loop_info(ffd, lfd, file, offset, sizelimit, flags);
+		rc = set_loop_info(ffd, lfd, &loopinfo);
 		if (rc == lfd) {
 			/* SUCCESS! */
 			if (!*device)
-- 
2.27.0

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