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blockdev-util: reopen file descriptor only when O_PATH is set

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Prompted by 13879c54d4.
This commit is contained in:
Yu Watanabe
2022-09-28 17:41:09 +09:00
parent 7e4a0387c4
commit 446f8db66b
1 changed files with 16 additions and 6 deletions
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src/shared/blockdev-util.c
+16 -6
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@@ -40,16 +40,26 @@ static int fd_get_devnum(int fd, bool backing, dev_t *ret) {
else if (major(st.st_dev) != 0)
devnum = st.st_dev;
else {
_cleanup_close_ int regfd = -1;
/* If major(st.st_dev) is zero, this might mean we are backed by btrfs, which needs special
* handing, to get the backing device node. */
regfd = fd_reopen(fd, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
if (regfd < 0)
return regfd;
r = fcntl(fd, F_GETFL);
if (r < 0)
return -errno;
r = btrfs_get_block_device_fd(regfd, &devnum);
if (FLAGS_SET(r, O_PATH)) {
_cleanup_close_ int regfd = -1;
/* The fstat() above we can execute on an O_PATH fd. But the btrfs ioctl we cannot.
* Hence acquire a "real" fd first, without the O_PATH flag. */
regfd = fd_reopen(fd, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
if (regfd < 0)
return regfd;
r = btrfs_get_block_device_fd(regfd, &devnum);
} else
r = btrfs_get_block_device_fd(fd, &devnum);
if (r == -ENOTTY) /* not btrfs */
return -ENOTBLK;
if (r < 0)