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loop: refactor: extract subfunction get_next_free_loop()

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Extract subfunction get_next_free_loop() from set_loop()

Also fix miss free(try) when stat(try) and mknod fail

function                                             old     new   delta
set_loop                                             807     790     -17

Fixes: 3448914e8cc5 ("mount,losetup: use /dev/loop-control is it exists")
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Xiaoming Ni 2022-12-12 18:41:02 +01:00 committed by Denys Vlasenko
parent 90456a6aa3
commit ddccf6cd2f
1 changed files with 26 additions and 30 deletions
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56
libbb/loop.c
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@ -96,6 +96,20 @@ int FAST_FUNC get_free_loop(void)
return loopdevno; /* can be -1 if error */
}
static int get_next_free_loop(char *dev, int id)
{
int loopdevno;
loopdevno = get_free_loop();
if (loopdevno != -1) {
/* loopdevno is -2 (use id) or >= 0 (use id = loopdevno): */
if (loopdevno >= 0)
id = loopdevno;
sprintf(dev, LOOP_FORMAT, id);
}
return loopdevno;
}
/* 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.
@ -123,30 +137,27 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
try = *device;
if (!try) {
get_free_loopN:
i = get_free_loop();
if (i == -1) {
close(ffd);
return -1; /* no free loop devices */
}
if (i >= 0) {
try = xasprintf(LOOP_FORMAT, i);
goto open_lfd;
}
/* i == -2: no /dev/loop-control. Do an old-style search for a free device */
try = dev;
}
/* Find a loop device */
/* 0xfffff is a max possible minor number in Linux circa 2010 */
for (i = 0; i <= 0xfffff; i++) {
sprintf(dev, LOOP_FORMAT, i);
if (!*device) {
rc = get_next_free_loop(dev, i);
if (rc == -1)
break; /* no free loop devices (or other error in LOOP_CTL_GET_FREE) */
if (rc >= 0)
/* /dev/loop-control gave us the next free /dev/loopN */
goto open_lfd;
/* else: sequential /dev/loopN, needs to be tested/maybe_created */
}
IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
&& errno == ENOENT
&& try == dev
&& (!*device)
) {
/* Node doesn't exist, try to create it */
if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
@ -179,13 +190,10 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
/* Associate free loop device with file */
if (ioctl(lfd, LOOP_SET_FD, ffd)) {
/* Ouch. Are we racing with other mount? */
if (!*device /* yes */
&& try != dev /* tried a _kernel-offered_ loopN? */
) {
free(try);
if (!*device) {
close(lfd);
//TODO: add "if (--failcount != 0) ..."?
goto get_free_loopN;
continue;
}
goto close_and_try_next_loopN;
}
@ -209,8 +217,6 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
}
if (rc == 0) {
/* SUCCESS! */
if (try != dev) /* tried a kernel-offered free loopN? */
*device = try; /* malloced */
if (!*device) /* was looping in search of free "/dev/loopN"? */
*device = xstrdup(dev);
rc = lfd; /* return this */
@ -218,16 +224,6 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
}
/* failure, undo LOOP_SET_FD */
ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
} else {
/* device is not free (rc == 0), or error other than ENXIO */
if (rc == 0 /* device is not free? */
&& !*device /* racing with other mount? */
&& try != dev /* tried a _kernel-offered_ loopN? */
) {
free(try);
close(lfd);
goto get_free_loopN;
}
}
close_and_try_next_loopN:
close(lfd);