ddccf6cd2
Xiaoming Ni
2022-12-12
Subject
loop: refactor: extract subfunction get_next_free_loop()
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libbb/loop.c+26 -30
| @@ -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); | |