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qga: flatten safe_open_or_create()

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There is a bit too much nesting in the function, this can be simplified
a bit to improve readability.

This also helps with the following error handling changes.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20220525144140.591926-5-marcandre.lureau@redhat.com>
This commit is contained in:
Marc-André Lureau 2022-05-25 16:41:29 +02:00
parent 56b6dab274
commit 69f56c140d
1 changed files with 63 additions and 63 deletions
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126
qga/commands-posix.c
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@ -339,73 +339,73 @@ find_open_flag(const char *mode_str, Error **errp)
static FILE *
safe_open_or_create(const char *path, const char *mode, Error **errp)
{
Error *local_err = NULL;
int oflag;
int fd = -1;
FILE *f = NULL;
oflag = find_open_flag(mode, &local_err);
if (local_err == NULL) {
int fd;
/* If the caller wants / allows creation of a new file, we implement it
* with a two step process: open() + (open() / fchmod()).
*
* First we insist on creating the file exclusively as a new file. If
* that succeeds, we're free to set any file-mode bits on it. (The
* motivation is that we want to set those file-mode bits independently
* of the current umask.)
*
* If the exclusive creation fails because the file already exists
* (EEXIST is not possible for any other reason), we just attempt to
* open the file, but in this case we won't be allowed to change the
* file-mode bits on the preexistent file.
*
* The pathname should never disappear between the two open()s in
* practice. If it happens, then someone very likely tried to race us.
* In this case just go ahead and report the ENOENT from the second
* open() to the caller.
*
* If the caller wants to open a preexistent file, then the first
* open() is decisive and its third argument is ignored, and the second
* open() and the fchmod() are never called.
*/
fd = open(path, oflag | ((oflag & O_CREAT) ? O_EXCL : 0), 0);
if (fd == -1 && errno == EEXIST) {
oflag &= ~(unsigned)O_CREAT;
fd = open(path, oflag);
}
if (fd == -1) {
error_setg_errno(&local_err, errno, "failed to open file '%s' "
"(mode: '%s')", path, mode);
} else {
qemu_set_cloexec(fd);
if ((oflag & O_CREAT) && fchmod(fd, DEFAULT_NEW_FILE_MODE) == -1) {
error_setg_errno(&local_err, errno, "failed to set permission "
"0%03o on new file '%s' (mode: '%s')",
(unsigned)DEFAULT_NEW_FILE_MODE, path, mode);
} else {
FILE *f;
f = fdopen(fd, mode);
if (f == NULL) {
error_setg_errno(&local_err, errno, "failed to associate "
"stdio stream with file descriptor %d, "
"file '%s' (mode: '%s')", fd, path, mode);
} else {
return f;
}
}
close(fd);
if (oflag & O_CREAT) {
unlink(path);
}
}
oflag = find_open_flag(mode, errp);
if (oflag < 0) {
goto end;
}
error_propagate(errp, local_err);
return NULL;
/* If the caller wants / allows creation of a new file, we implement it
* with a two step process: open() + (open() / fchmod()).
*
* First we insist on creating the file exclusively as a new file. If
* that succeeds, we're free to set any file-mode bits on it. (The
* motivation is that we want to set those file-mode bits independently
* of the current umask.)
*
* If the exclusive creation fails because the file already exists
* (EEXIST is not possible for any other reason), we just attempt to
* open the file, but in this case we won't be allowed to change the
* file-mode bits on the preexistent file.
*
* The pathname should never disappear between the two open()s in
* practice. If it happens, then someone very likely tried to race us.
* In this case just go ahead and report the ENOENT from the second
* open() to the caller.
*
* If the caller wants to open a preexistent file, then the first
* open() is decisive and its third argument is ignored, and the second
* open() and the fchmod() are never called.
*/
fd = open(path, oflag | ((oflag & O_CREAT) ? O_EXCL : 0), 0);
if (fd == -1 && errno == EEXIST) {
oflag &= ~(unsigned)O_CREAT;
fd = open(path, oflag);
}
if (fd == -1) {
error_setg_errno(errp, errno,
"failed to open file '%s' (mode: '%s')",
path, mode);
goto end;
}
qemu_set_cloexec(fd);
if ((oflag & O_CREAT) && fchmod(fd, DEFAULT_NEW_FILE_MODE) == -1) {
error_setg_errno(errp, errno, "failed to set permission "
"0%03o on new file '%s' (mode: '%s')",
(unsigned)DEFAULT_NEW_FILE_MODE, path, mode);
goto end;
}
f = fdopen(fd, mode);
if (f == NULL) {
error_setg_errno(errp, errno, "failed to associate stdio stream with "
"file descriptor %d, file '%s' (mode: '%s')",
fd, path, mode);
}
end:
if (f == NULL && fd != -1) {
close(fd);
if (oflag & O_CREAT) {
unlink(path);
}
}
return f;
}
int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode,