22.08.2019 21:55, Vladimir Sementsov-Ogievskiy wrote:
> 22.08.2019 21:31, Andrey Shinkevich wrote:
>> Revert the commit 118f99442d 'block/io.c: fix for the allocation failure'
>> and make better error handling for the file systems that do not support
>> fallocate() for the unaligned byte range. Allow falling back to pwrite
>> in case fallocate() returns EINVAL.
>>
>> Suggested-by: Kevin Wolf <kw...@redhat.com>
>> Suggested-by: Eric Blake <ebl...@redhat.com>
>> Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
>> ---
>> Discussed in email thread with the message ID
>> <1554474244-553661-1-git-send-email-andrey.shinkev...@virtuozzo.com>
>>
>> block/file-posix.c | 7 +++++++
>> block/io.c | 2 +-
>> 2 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index fbeb006..2c254ff 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -1588,6 +1588,13 @@ static int j(void *opaque)
>> if (s->has_write_zeroes) {
>> int ret = do_fallocate(s->fd, FALLOC_FL_ZERO_RANGE,
>> aiocb->aio_offset, aiocb->aio_nbytes);
>> + if (ret == -EINVAL) {
>> + /*
>> + * Allow falling back to pwrite for file systems that
>> + * do not support fallocate() for unaligned byte range.
>> + */
>> + return -ENOTSUP;
>> + }
>> if (ret == 0 || ret != -ENOTSUP) {
>> return ret;
>> }
>
> Hmm stop, you've done exactly what Den was afraid of:
>
> the next line
> s->has_write_zeroes = false;
>
> will disable write_zeroes forever.
>
> Something like
>
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1588,10 +1588,12 @@ static int handle_aiocb_write_zeroes(void *opaque)
> if (s->has_write_zeroes) {
> int ret = do_fallocate(s->fd, FALLOC_FL_ZERO_RANGE,
> aiocb->aio_offset, aiocb->aio_nbytes);
> - if (ret == 0 || ret != -ENOTSUP) {
> + if (ret == 0 || (ret != -ENOTSUP && ret != -EINVAL)) {
> return ret;
> }
> - s->has_write_zeroes = false;
> + if (ret == -ENOTSUP) {
> + s->has_write_zeroes = false;
> + }
> }
> #endif
>
>
> will work better. So, handle ENOTSUP as "disable write_zeros forever", and
> EINVAL as
> "don't disable, but fallback to writing zeros". And we need same handling for
> following do_fallocate() calls
> too (otherwise they again fails with EINVAL which will break the whole thing).
>
Oops, sorry, I misread your patch, it's OK.
Still we may want to handle other do_fallocate() calls in same manner, or may
be just:
@@ -1558,7 +1558,13 @@ static int coroutine_fn
bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
assert(!bs->supported_zero_flags);
}
- if (ret < 0 && !(flags & BDRV_REQ_NO_FALLBACK)) {
+ /*
+ * We are sure that our arguments make sense, so consider "invalid
+ * argument" in same manner as "not supported".
+ */
+ if ((ret == -ENOTSUP || ret == -EINVAL) &&
+ !(flags & BDRV_REQ_NO_FALLBACK))
+ {
/* Fall back to bounce buffer if write zeroes is unsupported */
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
--
Best regards,
Vladimir
