Re: [PATCH 9/9] loop: Add LOOP_CONFIGURE ioctl
On Fri, 18 Nov 2022 09:01:58 +0800 Xiaoming Ni wrote: > LOOP_CONFIGURE is added to Linux 5.8 ... > diff --git a/libbb/loop.c b/libbb/loop.c > index 9a7ca666d..d4f4906b0 100644 > --- a/libbb/loop.c > +++ b/libbb/loop.c > @@ -126,6 +126,30 @@ static int open_file(const char *file, unsigned flags, > int *mode) > return ffd; > } > > +#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0) > +static int set_loop_configure(int ffd, int lfd, bb_loop_info *loopinfo) > +#else This assumes compile-time matches runtime. Ie, if you build on a 5.8 system, but run on an earlier kernel, the resulting busybox would be unable to mount loops at all. Please put it backward runtime compatibility, probably by having the new-kernel code in the same func. - Lauri ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
[PATCH 8/9] loop:refactor: extract subfunction set_loop_dev()
Step 8 of micro-refactoring the set_loop():
Extract subfunction open_file() from set_loop_dev()
function old new delta
set_loop 700 703 +3
--
(add/remove: 0/0 grow/shrink: 1/0 up/down: 3/0) Total: 3 bytes
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 41 -
1 file changed, 24 insertions(+), 17 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 67e16ddb0..9a7ca666d 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -201,6 +201,26 @@ static int do_stat_and_mknod(const char *dev, const char
*device, int i)
return 0;
}
+static int set_loop_dev(const char *dev, int *mode, int ffd, bb_loop_info
*loopinfo)
+{
+ int rc;
+ /* Open the sucker and check its loopiness */
+ int lfd = open(dev, *mode);
+ if (lfd < 0 && errno == EROFS) {
+ *mode = O_RDONLY;
+ lfd = open(dev, *mode);
+ }
+ if (lfd < 0) {
+ return lfd;
+ }
+ rc = set_loop_info(ffd, lfd, loopinfo);
+ if (rc == lfd) {
+ return lfd;
+ }
+ close(lfd);
+ 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
@@ -211,7 +231,7 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
{
char dev[LOOP_NAMESIZE];
char *try;
- int i, lfd, ffd, mode, rc;
+ int i, ffd, mode, rc;
bb_loop_info loopinfo;
ffd = open_file(file, flags, );
@@ -242,32 +262,19 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
break;
}
open_lfd:
- /* Open the sucker and check its loopiness */
- lfd = rc = open(try, mode);
- if (lfd < 0 && errno == EROFS) {
- mode = O_RDONLY;
- lfd = rc = open(try, mode);
- }
- if (lfd < 0) {
+ rc = set_loop_dev(try, , ffd, );
+ if (rc == -1) {
if (errno == ENXIO) {
/* Happens if loop module is not loaded */
/* rc is -1; */
break;
}
- goto try_next_loopN;
- }
- rc = set_loop_info(ffd, lfd, );
- if (rc == lfd) {
+ } else {
/* SUCCESS! */
if (!*device)
*device = xstrdup(try);
break;
}
- close(lfd);
- try_next_loopN:
- rc = -1;
- if (*device) /* was looking for a particular "/dev/loopN"? */
- break; /* yes, do not try other names */
} /* for() */
close(ffd);
--
2.27.0
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[PATCH 1/9] loop:refactor: extract subfunction open_file()
Step 1 of micro-refactoring the set_loop():
Extract subfunction open_file() from set_loop()
function old new delta
set_loop 760 758 -2
--
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-2) Total: -2 bytes
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 25 +
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 750642ade..c517ceb13 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -96,6 +96,22 @@ int FAST_FUNC get_free_loop(void)
return loopdevno; /* can be -1 if error */
}
+static int open_file(const char *file, unsigned flags, int *mode)
+{
+ int ffd;
+ /* open the file. barf if this doesn't work. */
+ *mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
+ retry_open_ffd:
+ ffd = open(file, *mode);
+ if (ffd < 0) {
+ if (*mode != O_RDONLY) {
+ *mode = O_RDONLY;
+ goto retry_open_ffd;
+ }
+ }
+ return ffd;
+}
+
/* 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.
@@ -109,15 +125,8 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
struct stat statbuf;
int i, lfd, ffd, mode, rc;
- /* Open the file. Barf if this doesn't work. */
- mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
- open_ffd:
- ffd = open(file, mode);
+ ffd = open_file(file, flags, );
if (ffd < 0) {
- if (mode != O_RDONLY) {
- mode = O_RDONLY;
- goto open_ffd;
- }
return -errno;
}
--
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[PATCH 9/9] loop: Add LOOP_CONFIGURE ioctl
LOOP_CONFIGURE is added to Linux 5.8
This allows userspace to completely setup a loop device with a single
ioctl, removing the in-between state where the device can be partially
configured - eg the loop device has a backing file associated with it,
but is reading from the wrong offset.
https://lwn.net/Articles/820408/
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3448914e8cc5
LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0):
function old new delta
set_loop 703 626 -77
--
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-77) Total:
-77 bytes
else:
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 25 +
1 file changed, 25 insertions(+)
diff --git a/libbb/loop.c b/libbb/loop.c
index 9a7ca666d..d4f4906b0 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -126,6 +126,30 @@ static int open_file(const char *file, unsigned flags, int
*mode)
return ffd;
}
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0)
+
+/*
+ * loop: Add LOOP_CONFIGURE ioctl
+ * https://lwn.net/Articles/820408/
+ *
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3448914e8cc5
+ */
+static int set_loop_configure(int ffd, int lfd, bb_loop_info *loopinfo)
+{
+ int rc;
+ struct loop_config config;
+
+ memset(, 0, sizeof(config));
+ config.fd = ffd;
+ memcpy(, loopinfo, sizeof(config.info));
+
+ rc = ioctl(lfd, LOOP_CONFIGURE, );
+ if (rc == 0) {
+ return lfd;
+ }
+ return -1;
+}
+
+#else
static int set_loop_configure(int ffd, int lfd, bb_loop_info *loopinfo)
{
int rc;
@@ -149,6 +173,7 @@ static int set_loop_configure(int ffd, int lfd,
bb_loop_info *loopinfo)
ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
return -1;
}
+#endif
static int set_loop_info(int ffd, int lfd, bb_loop_info *loopinfo)
{
--
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[PATCH 3/9] loop:refactor: del close_and_try_next_loopN
Step 3 of micro-refactoring the set_loop() function:
Delete close_and_try_next_loopN.
(add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0) Total: 0 bytes
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 71fd8c1bc..91c3a45c4 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -197,13 +197,14 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
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) {
- close(lfd);
//TODO: add "if (--failcount != 0) ..."?
continue;
+ } else {
+ break;
}
- goto close_and_try_next_loopN;
}
memset(, 0, sizeof(loopinfo));
safe_strncpy((char *)loopinfo.lo_file_name, file,
LO_NAME_SIZE);
@@ -233,7 +234,6 @@ 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
}
- close_and_try_next_loopN:
close(lfd);
try_next_loopN:
rc = -1;
--
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[PATCH 7/9] loop:refactor: Extract subfunction do_stat_and_mknod()
Step 7 of micro-refactoring the set_loop():
Extract subfunction do_stat_and_mknod()
function old new delta
set_loop 720 700 -20
--
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-20) Total: -20 bytes
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 39 +--
1 file changed, 25 insertions(+), 14 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 2200ccb9a..67e16ddb0 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -180,6 +180,28 @@ static void init_bb_loop_info(bb_loop_info *loopinfo,
const char *file,
loopinfo->lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
}
+static int do_stat_and_mknod(const char *dev, const char *device, int i)
+{
+ struct stat statbuf;
+
+ IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
+ if (stat(dev, ) != 0 || !S_ISBLK(statbuf.st_mode)) {
+ if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
+ && errno == ENOENT
+ && (!device)
+ ) {
+ /* Node doesn't exist, try to create it */
+ if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0) {
+ return 0;
+ }
+ }
+ /* Ran out of block devices, return failure */
+ return -1;
+ }
+ return 0;
+}
+
+
/* 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.
@@ -189,7 +211,6 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
{
char dev[LOOP_NAMESIZE];
char *try;
- struct stat statbuf;
int i, lfd, ffd, mode, rc;
bb_loop_info loopinfo;
@@ -216,18 +237,8 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
}
}
- IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
- if (stat(try, ) != 0 || !S_ISBLK(statbuf.st_mode)) {
- if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
-&& errno == ENOENT
-&& (!*device)
- ) {
- /* Node doesn't exist, try to create it */
- if (mknod(dev, S_IFBLK|0644, makedev(7, i)) ==
0)
- goto open_lfd;
- }
- /* Ran out of block devices, return failure */
- rc = -1;
+ rc = do_stat_and_mknod(try, *device, i);
+ if (rc == -1) {
break;
}
open_lfd:
@@ -249,7 +260,7 @@ int FAST_FUNC set_loop(char **device, const char *file,
unsigned long long offse
if (rc == lfd) {
/* SUCCESS! */
if (!*device)
- *device = xstrdup(dev);
+ *device = xstrdup(try);
break;
}
close(lfd);
--
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[PATCH 5/9] loop:refactor: extract subfunction set_loop_configure()
Step 5 of micro-refactoring the set_loop():
Extract subfunction set_loop_configure()
function old new delta
set_loop 700 708 +8
--
(add/remove: 0/0 grow/shrink: 1/0 up/down: 8/0) Total: 8 bytes
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 63 ++--
1 file changed, 36 insertions(+), 27 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 89adc4f94..914af57b2 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -126,6 +126,41 @@ 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)
+{
+ int rc;
+ bb_loop_info loopinfo;
+ /* Associate free loop device with file */
+ if (ioctl(lfd, LOOP_SET_FD, ffd)) {
+ return -1;
+ }
+ memset(, 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, );
+ 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, );
+ }
+ if (rc == 0) {
+ return lfd;
+ }
+ /* failure, undo LOOP_SET_FD */
+ ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+ return -1;
+}
+
static int set_loop_info(int ffd, int lfd, const char *file,
unsigned long long offset, unsigned long long sizelimit,
unsigned flags)
{
@@ -136,33 +171,7 @@ static int set_loop_info(int ffd, int lfd, const char
*file,
/* 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(, 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, );
- 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, );
- }
- if (rc == 0) {
- return lfd;
- }
- /* failure, undo LOOP_SET_FD */
- ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+ return set_loop_configure(ffd, lfd, file, offset, sizelimit,
flags);
}
return -1;
}
--
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[PATCH 2/9] loop:refactor: extract subfunction get_next_free_loop()
Step 2 of micro-refactoring the set_loop function ()
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 758 734 -24
--
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-24) Total: -24 bytes
Fixes: 3448914e8cc5 ("mount,losetup: use /dev/loop-control is it exists")
Signed-off-by: Xiaoming Ni
---
libbb/loop.c | 55
1 file changed, 25 insertions(+), 30 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index c517ceb13..71fd8c1bc 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -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 i = get_free_loop();
+ if (i >= 0) {
+ sprintf(dev, LOOP_FORMAT, i);
+ return 1; /* use /dev/loop-control */
+ } else if (i == -2) {
+ sprintf(dev, LOOP_FORMAT, id);
+ return 2;
+ } else {
+ return -1; /* no free loop devices */
+ }
+}
+
static int open_file(const char *file, unsigned flags, int *mode)
{
int ffd;
@@ -132,30 +146,26 @@ 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 */
/* 0xf is a max possible minor number in Linux circa 2010 */
for (i = 0; i <= 0xf; i++) {
- sprintf(dev, LOOP_FORMAT, i);
+ if (!*device) {
+ rc = get_next_free_loop(dev, i);
+ if (rc == -1) {
+ break; /* no free loop devices */
+ } else if (rc == 1) {
+ goto open_lfd;
+ }
+ }
IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
if (stat(try, ) != 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)
@@ -188,13 +198,10 @@ 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;
}
@@ -218,8 +225,6 @@ 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 */
@@ -227,16 +232,6 @@ 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
[PATCH 4/9] loop:refactor: extract subfunction set_loop_info()
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
---
libbb/loop.c | 91 +++-
1 file changed, 47 insertions(+), 44 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 91c3a45c4..89adc4f94 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, );
+
+ /* 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(, 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, );
+ 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, );
+ }
+ 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, );
-
- /* 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(, 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, );
- if (rc != 0 && (loopinfo.lo_flags &
BB_LO_FLAGS_AUTOCLEAR)) {
- /* Old kernel, does not support
LO_FLAGS_AUTOCLEAR? */
- /* (this code path is not tested) */
-
[PATCH 6/9] loop:refactor: Use a structure to reduce parameters
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
---
libbb/loop.c | 54 +---
1 file changed, 30 insertions(+), 24 deletions(-)
diff --git a/libbb/loop.c b/libbb/loop.c
index 914af57b2..2200ccb9a 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(, 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, );
- 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(, 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, );
+ loopinfo2.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
+ rc = ioctl(lfd, BB_LOOP_SET_STATUS, );
}
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, );
+ rc = ioctl(lfd, BB_LOOP_GET_STATUS, );
/* 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, );
if (ffd < 0) {
return -errno;
}
+ init_bb_loop_info(, 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);
+
[PATCH 0/9] loop: Micro-refactoring set_loop() and add LOOP_CONFIGURE
LOOP_CONFIGURE is added to Linux 5.8 This allows userspace to completely setup a loop device with a single ioctl, removing the in-between state where the device can be partially configured - eg the loop device has a backing file associated with it, but is reading from the wrong offset. https://lwn.net/Articles/820408/ https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3448914e8cc5 To facilitate the addition of new functions, the code of set_loop() is micro-refactored. LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0): function old new delta set_loop 760 626-134 -- (add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-134) Total: -134 bytes else function old new delta set_loop 760 703 -57 -- (add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-57) Total: -57 bytes Xiaoming Ni (9): loop:refactor: extract subfunction open_file() loop:refactor: extract subfunction get_next_free_loop() loop:refactor: del close_and_try_next_loopN loop:refactor: extract subfunction set_loop_info() loop:refactor: extract subfunction set_loop_configure() loop:refactor: Use a structure to reduce parameters loop:refactor: Extract subfunction do_stat_and_mknod() loop:refactor: extract subfunction set_loop_dev() loop: Add LOOP_CONFIGURE ioctl libbb/loop.c | 275 +++ 1 file changed, 170 insertions(+), 105 deletions(-) -- 2.27.0 ___ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
