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From: Kanchan Joshi <[email protected]>
To: Matthew Wilcox <[email protected]>
Cc: Christoph Hellwig <[email protected]>,
	Jens Axboe <[email protected]>, Kanchan Joshi <[email protected]>,
	[email protected], [email protected], [email protected],
	[email protected], [email protected],
	"Matias Bj??rling" <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	Selvakumar S <[email protected]>,
	Nitesh Shetty <[email protected]>,
	Javier Gonzalez <[email protected]>
Subject: Re: [PATCH v3 4/4] io_uring: add support for zone-append
Date: Mon, 20 Jul 2020 22:19:57 +0530	[thread overview]
Message-ID: <CA+1E3r+j=amkEg-_KUKSiu6gt2TRU6AU-_jwnB1C6wHHKnptfQ@mail.gmail.com> (raw)
In-Reply-To: <CA+1E3rKOZUz7oZ_DGW6xZPQaDu+T5iEKXctd+gsJw05VwpGQSQ@mail.gmail.com>

On Fri, Jul 10, 2020 at 7:41 PM Kanchan Joshi <[email protected]> wrote:
>
> On Fri, Jul 10, 2020 at 7:21 PM Matthew Wilcox <[email protected]> wrote:
> >
> > On Fri, Jul 10, 2020 at 02:49:32PM +0100, Christoph Hellwig wrote:
> > > On Fri, Jul 10, 2020 at 02:48:24PM +0100, Matthew Wilcox wrote:
> > > > If we're going to go the route of changing the CQE, how about:
> > > >
> > > >  struct io_uring_cqe {
> > > >          __u64   user_data;      /* sqe->data submission passed back */
> > > > -        __s32   res;            /* result code for this event */
> > > > -        __u32   flags;
> > > > +   union {
> > > > +           struct {
> > > > +                   __s32   res;            /* result code for this event */
> > > > +                   __u32   flags;
> > > > +           };
> > > > +           __s64   res64;
> > > > +   };
> > > >  };
> > > >
> > > > then we don't need to change the CQE size and it just depends on the SQE
> > > > whether the CQE for it uses res+flags or res64.
> > >
> > > How do you return a status code or short write when you just have
> > > a u64 that is needed for the offset?
> >
> > it's an s64 not a u64 so you can return a negative errno.  i didn't
> > think we allowed short writes for objects-which-have-a-pos.
>
> If we are doing this for zone-append (and not general cases), "__s64
> res64" should work -.
> 64 bits = 1 (sign) + 23 (bytes-copied: cqe->res) + 40
> (written-location: chunk_sector bytes limit)

And this is for the scheme when single CQE is used with bits
refactoring into "_s64 res64" instead of res/flags.

41 bits for zone-append completion = in bytes, sufficient to cover
chunk_sectors size zone
1+22 bits for zone-append bytes-copied = can cover 4MB bytes copied
(single I/O is capped at 4MB in NVMe)

+ * zone-append specific flags
+#define APPEND_OFFSET_BITS     (41)
+#define APPEND_RES_BITS                (23)
+
+/*
  * IO completion data structure (Completion Queue Entry)
  */
 struct io_uring_cqe {
-       __u64   user_data;      /* sqe->data submission passed back */
-       __s32   res;            /* result code for this event */
-       __u32   flags;
+       __u64   user_data;      /* sqe->data submission passed back */
+        union {
+                struct {
+                        __s32   res;            /* result code for
this event */
+                        __u32   flags;
+                };
+               /* Alternate for zone-append */
+               struct {
+                       union {
+                               /*
+                                * kernel uses this to store append result
+                                * Most significant 23 bits to return number of
+                                * bytes or error, and least significant 41 bits
+                                * to return zone-relative offset in bytes
+                                * */
+                               __s64 res64;
+                               /*for user-space ease, kernel does not use*/
+                               struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+                                       __u64 append_offset :
APPEND_OFFSET_BITS;
+                                       __s32 append_res : APPEND_RES_BITS;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+                                       __s32 append_res : APPEND_RES_BITS;
+                                       __u64 append_offset :
APPEND_OFFSET_BITS;
+#endif
+                               }__attribute__ ((__packed__));
+                       };
+                };
+        };
 };

-- 
Joshi

  reply	other threads:[~2020-07-20 16:50 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200705185204epcas5p3adeb4fc3473c5fc0472a7396783c5267@epcas5p3.samsung.com>
2020-07-05 18:47 ` [PATCH v3 0/4] zone-append support in io-uring and aio Kanchan Joshi
     [not found]   ` <CGME20200705185211epcas5p4059d05d2fcedb91829300a7a7d03fda3@epcas5p4.samsung.com>
2020-07-05 18:47     ` [PATCH v3 1/4] fs: introduce FMODE_ZONE_APPEND and IOCB_ZONE_APPEND Kanchan Joshi
     [not found]   ` <CGME20200705185217epcas5p1cc12d4b892f057a1fe06d73a00869daa@epcas5p1.samsung.com>
2020-07-05 18:47     ` [PATCH v3 2/4] block: add zone append handling for direct I/O path Kanchan Joshi
     [not found]   ` <CGME20200705185221epcas5p28b6d060df829b751109265222285da0e@epcas5p2.samsung.com>
2020-07-05 18:47     ` [PATCH v3 3/4] block: enable zone-append for iov_iter of bvec type Kanchan Joshi
     [not found]   ` <CGME20200705185227epcas5p16fba3cb92561794b960184c89fdf2bb7@epcas5p1.samsung.com>
2020-07-05 18:47     ` [PATCH v3 4/4] io_uring: add support for zone-append Kanchan Joshi
2020-07-05 21:00       ` Jens Axboe
2020-07-05 21:09         ` Matthew Wilcox
2020-07-05 21:12           ` Jens Axboe
2020-07-06 14:10             ` Matthew Wilcox
2020-07-06 14:27               ` Jens Axboe
2020-07-06 14:32                 ` Matthew Wilcox
2020-07-06 14:33                   ` Jens Axboe
2020-07-07 15:11                   ` Kanchan Joshi
2020-07-07 15:52                     ` Matthew Wilcox
2020-07-07 16:00                       ` Christoph Hellwig
2020-07-07 20:23                       ` Kanchan Joshi
2020-07-07 20:40                         ` Jens Axboe
2020-07-07 22:18                           ` Matthew Wilcox
2020-07-07 22:37                             ` Jens Axboe
2020-07-08 12:58                               ` Kanchan Joshi
2020-07-08 14:22                                 ` Matthew Wilcox
2020-07-08 16:41                                   ` Kanchan Joshi
2020-07-08 14:54                                 ` Jens Axboe
2020-07-08 14:58                                   ` Matthew Wilcox
2020-07-08 14:59                                     ` Jens Axboe
2020-07-08 15:02                                       ` Matthew Wilcox
2020-07-08 15:06                                         ` Jens Axboe
2020-07-08 16:08                                           ` Javier González
2020-07-08 16:33                                             ` Matthew Wilcox
2020-07-08 16:38                                               ` Jens Axboe
2020-07-08 17:13                                                 ` Kanchan Joshi
2020-07-08 16:43                                               ` Javier González
2020-07-06 13:58         ` Kanchan Joshi
2020-07-09 10:15         ` Christoph Hellwig
2020-07-09 13:58           ` Jens Axboe
2020-07-09 14:00             ` Christoph Hellwig
2020-07-09 14:05               ` Jens Axboe
2020-07-09 18:36                 ` Kanchan Joshi
2020-07-09 18:50                   ` Pavel Begunkov
2020-07-09 18:53                     ` Pavel Begunkov
2020-07-09 18:50                   ` Jens Axboe
2020-07-09 19:05                     ` Kanchan Joshi
2020-07-10 13:10                       ` Christoph Hellwig
2020-07-10 13:48                         ` Matthew Wilcox
2020-07-10 13:49                           ` Christoph Hellwig
2020-07-10 13:51                             ` Matthew Wilcox
2020-07-10 14:11                               ` Kanchan Joshi
2020-07-20 16:49                                 ` Kanchan Joshi [this message]
2020-07-20 17:14                                   ` Matthew Wilcox
2020-07-20 20:17                                     ` Kanchan Joshi
2020-07-21  0:59                                       ` Damien Le Moal
2020-07-21  1:15                                         ` Matthew Wilcox
2020-07-21  1:29                                           ` Jens Axboe
2020-07-21  2:19                                           ` Damien Le Moal
2020-07-10 14:09                         ` Jens Axboe
2020-07-20 16:46                           ` Kanchan Joshi
2020-07-10 13:09                     ` Christoph Hellwig
2020-07-10 13:29                       ` Kanchan Joshi
2020-07-10 13:43                         ` Christoph Hellwig
2020-07-20 17:02                           ` Kanchan Joshi
2020-07-10 13:57                         ` Kanchan Joshi

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