On 04/10/2015 05:50 PM, Ming Lin wrote:
On Wed, Mar 25, 2015 at 7:26 AM, Jens Axboe <axboe@xxxxxxxxx> 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 <axboe@xxxxxx>
---
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
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