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Re: [Qemu-block] [Qemu-devel] [PATCH for-2.10 07/16] block/file-posix: G
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH for-2.10 07/16] block/file-posix: Generalize raw_regular_truncate |
Date: |
Mon, 20 Mar 2017 16:11:24 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
On 20.03.2017 12:00, Stefan Hajnoczi wrote:
> On Mon, Mar 13, 2017 at 10:40:36PM +0100, Max Reitz wrote:
>> Currently, raw_regular_truncate() is intended for setting the size of a
>> newly created file. However, we also want to use it for truncating an
>> existing file in which case only the newly added space (when growing)
>> should be preallocated.
>>
>> This also means that if resizing failed, we should try to restore the
>> original file size. This is important when using preallocation.
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>> block/file-posix.c | 73
>> ++++++++++++++++++++++++++++++++++++++++++++----------
>> 1 file changed, 60 insertions(+), 13 deletions(-)
>>
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index 35a9e43f3e..cd229324ba 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -1384,11 +1384,39 @@ static void raw_close(BlockDriverState *bs)
>> }
>> }
>>
>> -static int raw_regular_truncate(int fd, int64_t offset, PreallocMode
>> prealloc,
>> +/**
>> + * Truncates the given regular file @fd to @offset and, when growing, fills
>> the
>> + * new space according to @prealloc.
>> + *
>> + * @create must be true iff the file is new. In that case, @bs is ignored.
>> If
>> + * @create is false, @bs must be valid and correspond to the same file as
>> @fd.
>
> Returns: 0 on success, -errno on failure.
Yep, will add.
>> + */
>> +static int raw_regular_truncate(int fd, BlockDriverState *bs, int64_t
>> offset,
>
> The presence of both a file descriptor and a BlockDriverState (actually
> it must be a BDRVRawState) arguments is unusual. It seems bs is needed
> for bdrv_getlength().
>
> How about using fstat(fd, &st) and then dropping bs and create?
Well, I could do that, but bdrv_getlength() is a bit simpler and I don't
see much of an issue with specifying both an fd and a bs.
>> + PreallocMode prealloc, bool create,
>> Error **errp)
>> {
>> int result = 0;
>> - char *buf;
>> + int64_t current_length = 0;
>> + char *buf = NULL;
>> +
>> + assert(create || bs);
>> + if (!create) {
>> + BDRVRawState *s = bs->opaque;
>> + assert(s->fd == fd);
>> + }
>> +
>> + if (!create) {
>> + current_length = bdrv_getlength(bs);
>> + if (current_length < 0) {
>> + error_setg_errno(errp, -current_length,
>> + "Could not inquire current length");
>> + return -current_length;
>> + }
>> +
>> + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
>> + return -ENOTSUP;
>> + }
>
> Missing error_setg().
Indeed! Will fix.
Max
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- Re: [Qemu-block] [PATCH for-2.10 03/16] block: Add PreallocMode to blk_truncate(), (continued)
[Qemu-block] [PATCH for-2.10 08/16] block/file-posix: Preallocation for truncate, Max Reitz, 2017/03/13
[Qemu-block] [PATCH for-2.10 09/16] block/qcow2: Generalize preallocate(), Max Reitz, 2017/03/13
[Qemu-block] [PATCH for-2.10 10/16] block/qcow2: Lock s->lock in preallocate(), Max Reitz, 2017/03/13