On 07/19/2014 04:02 AM, loody wrote: > hi Randy: > > 2014-07-19 2:13 GMT+08:00 Randy Dunlap <rdunlap@xxxxxxxxxxxxx>: >> On 07/18/2014 10:31 AM, loody wrote: >>> hi Randy and All: >>> >>>> >>>> It means that the <buffer> still is not aligned to a 512-byte boundary. >>>> Try >>>> char buffer[1024] __attribute__ ((aligned(1024))); >>>> >>>> Well, that is aligned to 1024 bytes, not 512, but whatever. >>> the suggestion you gave to me works ^^ >>> is there any alignment check in kernel FS such that it will directly >>> output to device instead of getting data from page cache? >> >> Not sure that I understand your question, but I think that using >> O_DIRECT in the open() call attempts to do what you are asking. >> >> Please read 'man open' and search for O_DIRECT. > sorry for making you confused. ^^ > I just want to know why O_DIRECT is not enough and need to announce > the buffer size as 512-byte boundary. > > Is there any checking mechanism for 512-byte when O_DIRECT flag apply? Sorry, I have no idea. -- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
