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loop-util: add new loop_device_make_by_path_memory() helper

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This uses the new memfd_clone_fd() call to make an in-memory copy of
some file before setting up a loopback block device on it.
This commit is contained in:
Lennart Poettering 2022-12-08 12:45:48 +01:00
parent 6bea3d8e0f
commit fcd8a19da8
2 changed files with 43 additions and 0 deletions
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42
src/shared/loop-util.c
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@ -17,6 +17,7 @@
#include "alloc-util.h"
#include "blockdev-util.h"
#include "data-fd-util.h"
#include "device-util.h"
#include "devnum-util.h"
#include "env-util.h"
@ -640,6 +641,47 @@ int loop_device_make_by_path(
return loop_device_make_internal(path, fd, open_flags, 0, 0, 0, loop_flags, lock_op, ret);
}
int loop_device_make_by_path_memory(
const char *path,
int open_flags,
uint32_t loop_flags,
int lock_op,
LoopDevice **ret) {
_cleanup_close_ int fd = -EBADF, mfd = -EBADF;
_cleanup_free_ char *fn = NULL;
struct stat st;
int r;
assert(path);
assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
assert(ret);
loop_flags &= ~LO_FLAGS_DIRECT_IO; /* memfds don't support O_DIRECT, hence LO_FLAGS_DIRECT_IO can't be used either */
fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_RDONLY);
if (fd < 0)
return -errno;
if (fstat(fd, &st) < 0)
return -errno;
if (!S_ISREG(st.st_mode) && !S_ISBLK(st.st_mode))
return -EBADF;
r = path_extract_filename(path, &fn);
if (r < 0)
return r;
mfd = memfd_clone_fd(fd, fn, open_flags|O_CLOEXEC);
if (mfd < 0)
return mfd;
fd = safe_close(fd); /* Let's close the original early */
return loop_device_make_internal(NULL, mfd, open_flags, 0, 0, 0, loop_flags, lock_op, ret);
}
static LoopDevice* loop_device_free(LoopDevice *d) {
_cleanup_close_ int control = -1;
int r;

1
src/shared/loop-util.h
View File

@ -30,6 +30,7 @@ struct LoopDevice {
int loop_device_make(int fd, int open_flags, uint64_t offset, uint64_t size, uint32_t block_size, uint32_t loop_flags, int lock_op, LoopDevice **ret);
int loop_device_make_by_path(const char *path, int open_flags, uint32_t loop_flags, int lock_op, LoopDevice **ret);
int loop_device_make_by_path_memory(const char *path, int open_flags, uint32_t loop_flags, int lock_op, LoopDevice **ret);
int loop_device_open(sd_device *dev, int open_flags, int lock_op, LoopDevice **ret);
int loop_device_open_from_fd(int fd, int open_flags, int lock_op, LoopDevice **ret);
int loop_device_open_from_path(const char *path, int open_flags, int lock_op, LoopDevice **ret);