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Re: [Qemu-block] [PATCH v2] file-posix: specify expected filetypes
From: |
John Snow |
Subject: |
Re: [Qemu-block] [PATCH v2] file-posix: specify expected filetypes |
Date: |
Wed, 17 Jan 2018 11:00:25 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 |
On 01/17/2018 05:45 AM, Kevin Wolf wrote:
> Am 15.01.2018 um 23:50 hat John Snow geschrieben:
>> I don't think there's a legitimate reason to open directories as if
>> they were files. This prevents QEMU from opening and attempting to probe
>> a directory inode, which can break in exciting ways. One of those ways
>> is lseek on ext4/xfs, which will return 0x7fffffffffffffff as the file
>> size instead of EISDIR. This can coax QEMU into responding with a
>> confusing "file too big" instead of "Hey, that's not a file".
>>
>> See: https://bugs.launchpad.net/qemu/+bug/1739304/
>> Signed-off-by: John Snow <address@hidden>
>> ---
>>
>> v2: Is something like this what you had in mind, Kevin?
>> I couldn't make the hdev/cdrom checks more specific
>> as I'm not sure which environments expect which, but
>> if you know I can tighten it.
>
> This should do. We could in theory be more specific about which OS
> expects block devices and which one uses character devices, but there's
> probably no point in doing that. And without further research I couldn't
> say much more than that Linux uses block devices and FreeBSD character
> devices.
>
The risk of breaking something stupid seems worse than the benefit of
tightening this.
(Also I don't want to install Solaris.)
>> block/file-posix.c | 38 +++++++++++++++++++++++++++++---------
>> 1 file changed, 29 insertions(+), 9 deletions(-)
>
> As Eric said, it would be good to add a deprecation note to
> qemu-doc.texi (and probably also the changelog in the wiki).
>
Yeah, sure thing.
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index 36ee89e940..fe06cdb8f8 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -417,7 +417,8 @@ static QemuOptsList raw_runtime_opts = {
>> };
>>
>> static int raw_open_common(BlockDriverState *bs, QDict *options,
>> - int bdrv_flags, int open_flags, Error **errp)
>> + int bdrv_flags, int open_flags,
>> + bool device, Error **errp)
>> {
>> BDRVRawState *s = bs->opaque;
>> QemuOpts *opts;
>> @@ -556,10 +557,30 @@ static int raw_open_common(BlockDriverState *bs, QDict
>> *options,
>> error_setg_errno(errp, errno, "Could not stat file");
>> goto fail;
>> }
>> - if (S_ISREG(st.st_mode)) {
>> - s->discard_zeroes = true;
>> - s->has_fallocate = true;
>> +
>> + if (!device) {
>> + if (S_ISBLK(st.st_mode)) {
>> + warn_report("Opening a block device as file using 'file'"
>> + "driver is deprecated");
>
> All your line-wrapped strings are missing a space at the end of the
> first line.
>
> Kevin
>
Oh, duh.