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file-posix: Support auto-read-only option

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If read-only=off, but auto-read-only=on is given, open the file
read-write if we have the permissions, but instead of erroring out for
read-only files, just degrade to read-only.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2018-10-08 17:27:18 +02:00
parent 6c2e581d4d
commit 64107dc044
1 changed files with 16 additions and 3 deletions
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19
block/file-posix.c
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@ -527,9 +527,22 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
s->fd = -1;
fd = qemu_open(filename, s->open_flags, 0644);
if (fd < 0) {
ret = -errno;
error_setg_errno(errp, errno, "Could not open '%s'", filename);
ret = fd < 0 ? -errno : 0;
if (ret == -EACCES || ret == -EROFS) {
/* Try to degrade to read-only, but if it doesn't work, still use the
* normal error message. */
if (bdrv_apply_auto_read_only(bs, NULL, NULL) == 0) {
bdrv_flags &= ~BDRV_O_RDWR;
raw_parse_flags(bdrv_flags, &s->open_flags);
assert(!(s->open_flags & O_CREAT));
fd = qemu_open(filename, s->open_flags);
ret = fd < 0 ? -errno : 0;
}
}
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not open '%s'", filename);
if (ret == -EROFS) {
ret = -EACCES;
}