On 04/10/2015 05:50 PM, Ming Lin wrote:
On Wed, Mar 25, 2015 at 7:26 AM, Jens Axboe <[email protected]> wrote:On 03/24/2015 08:43 PM, Dave Chinner wrote:On Tue, Mar 24, 2015 at 09:27:00AM -0600, Jens Axboe wrote:Get the streamid from the file, if any, and set it on the bio. Signed-off-by: Jens Axboe <[email protected]> --- fs/direct-io.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/direct-io.c b/fs/direct-io.c index e181b6b2e297..5d2750346451 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -77,6 +77,7 @@ struct dio_submit { int reap_counter; /* rate limit reaping */ sector_t final_block_in_request;/* doesn't change */ int boundary; /* prev block is at a boundary */ + int streamid; /* Write stream ID */ get_block_t *get_block; /* block mapping function */ dio_submit_t *submit_io; /* IO submition function */ @@ -372,6 +373,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, sdio->bio = bio; sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; + + bio_set_streamid(bio, sdio->streamid); } /* @@ -1205,6 +1208,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, sdio.blkbits = blkbits; sdio.blkfactor = i_blkbits - blkbits; sdio.block_in_file = offset >> blkbits; + sdio.streamid = iocb->ki_filp->f_streamid;If iocb->ki_filp->f_streamid is not set, then it should fall back to whatever is set on the inode->i_streamid.Why should do the fall back?
Because the assumption is that, in general, the specific file is a good indication of the data lifetime, if someone has already set that. It's a better guess than writing without any stream attached.
That change causes problem for direct IO, for example
process 1:
fd = open("/dev/nvme0n1", O_DIRECT...);
//set stream_id 1
fadvise(fd, 1, 0, POSIX_FADV_STREAMID);
pwrite(fd, ....);
process 2:
fd = open("/dev/nvme0n1", O_DIRECT...);
//should be legacy stream_id 0
pwrite(fd, ....);
But now process 2 also see stream_id 1, which is wrong.
I guess for that case, it is a problem. Basically the fallback breaks down for full block devices, or huge files that are used as a general backing store (like a vm image, for instance). Hmm, not sure what the right solution would be here, or if there really is one. It's probably best NOT to do the fallback after all.
-- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
