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loop-util: Add loop_device_make_by_path_at()

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On top of taking a directory file descriptor, we use xopenat() so
that the function can also be used to work on existing file
descriptors to image files including all the logic to use O_DIRECT
and fallback to O_RDONLY if needed.
This commit is contained in:
Daan De Meyer
2023-03-23 17:36:17 +01:00
parent 06ca2db39d
commit 972c8db589
2 changed files with 24 additions and 7 deletions
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src/shared/loop-util.c
+18 -6
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@@ -24,6 +24,7 @@
#include "env-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fs-util.h"
#include "fileio.h"
#include "loop-util.h"
#include "missing_loop.h"
@@ -650,7 +651,8 @@ int loop_device_make(
ret);
}
int loop_device_make_by_path(
int loop_device_make_by_path_at(
int dir_fd,
const char *path,
int open_flags,
uint32_t sector_size,
@@ -662,6 +664,7 @@ int loop_device_make_by_path(
_cleanup_close_ int fd = -EBADF;
bool direct = false;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
assert(path);
assert(ret);
assert(open_flags < 0 || IN_SET(open_flags, O_RDWR, O_RDONLY));
@@ -678,9 +681,9 @@ int loop_device_make_by_path(
direct_flags = FLAGS_SET(loop_flags, LO_FLAGS_DIRECT_IO) ? O_DIRECT : 0;
rdwr_flags = open_flags >= 0 ? open_flags : O_RDWR;
fd = open(path, basic_flags|direct_flags|rdwr_flags);
fd = xopenat(dir_fd, path, basic_flags|direct_flags|rdwr_flags, 0);
if (fd < 0 && direct_flags != 0) /* If we had O_DIRECT on, and things failed with that, let's immediately try again without */
fd = open(path, basic_flags|rdwr_flags);
fd = xopenat(dir_fd, path, basic_flags|rdwr_flags, 0);
else
direct = direct_flags != 0;
if (fd < 0) {
@@ -690,9 +693,9 @@ int loop_device_make_by_path(
if (open_flags >= 0 || !(ERRNO_IS_PRIVILEGE(r) || r == -EROFS))
return r;
fd = open(path, basic_flags|direct_flags|O_RDONLY);
fd = xopenat(dir_fd, path, basic_flags|direct_flags|O_RDONLY, 0);
if (fd < 0 && direct_flags != 0) /* as above */
fd = open(path, basic_flags|O_RDONLY);
fd = xopenat(dir_fd, path, basic_flags|O_RDONLY, 0);
else
direct = direct_flags != 0;
if (fd < 0)
@@ -709,7 +712,16 @@ int loop_device_make_by_path(
direct ? "enabled" : "disabled",
direct != (direct_flags != 0) ? " (O_DIRECT was requested but not supported)" : "");
return loop_device_make_internal(path, fd, open_flags, 0, 0, sector_size, loop_flags, lock_op, ret);
return loop_device_make_internal(
dir_fd == AT_FDCWD ? path : NULL,
fd,
open_flags,
/* offset = */ 0,
/* size = */ 0,
sector_size,
loop_flags,
lock_op,
ret);
}
int loop_device_make_by_path_memory(