From: David Sterba <dsterba@suse.cz>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Kent Overstreet <kent.overstreet@linux.dev>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-bcachefs@vger.kernel.org
Subject: Re: [GIT PULL] bcachefs
Date: Thu, 7 Sep 2023 01:13:54 +0200 [thread overview]
Message-ID: <20230906231354.GX14420@twin.jikos.cz> (raw)
In-Reply-To: <ZPj1WuwKKnvVEZnl@kernel.org>
On Wed, Sep 06, 2023 at 06:55:38PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Sep 06, 2023 at 01:20:59PM -0700, Linus Torvalds escreveu:
> > On Wed, 6 Sept 2023 at 13:02, Linus Torvalds
> > <torvalds@linux-foundation.org> wrote:
> > >
> > > And guess what happens when you have (unsigned char)-1? It does *not*
> > > cast back to -1.
> >
> > Side note: again, this may be one of those "it works in practice",
> > because if we have -fshort-enums, I think 'enum
> > btree_node_locked_type' in turn ends up being represented as a 'signed
> > char', because that's the smallest simple type that can fit all those
> > values.
>
> > I don't think gcc ever uses less than that (ie while a six_lock_type
> > could fit in two bits, it's still going to be considered at least a
> > 8-bit value in practice).
>
> There are some cases where people stuff the enum into a bitfield, but
> no, no simple type.
>
> ⬢[acme@toolbox perf-tools-next]$ pahole | grep -w enum | grep :
> enum btrfs_rsv_type type:8; /* 28:16 4 */
> enum btrfs_delayed_item_type type:8; /* 100: 0 4 */
The simple grep might give a skewed view, in the above case there's also
/* Bitfield combined with previous fields */
in the full output, with adjacent bool struct members it's all packed
into one int. I think I've always seen an int for enums, unless it was
explicitly narrowed in the structure (:8) or by __packed attribute in
the enum definition.
> enum kernel_pkey_operation op:8; /* 40: 0 4 */
> enum integrity_status ima_file_status:4; /* 96: 0 4 */
> enum integrity_status ima_mmap_status:4; /* 96: 4 4 */
> enum integrity_status ima_bprm_status:4; /* 96: 8 4 */
> enum integrity_status ima_read_status:4; /* 96:12 4 */
> enum integrity_status ima_creds_status:4; /* 96:16 4 */
> enum integrity_status evm_status:4; /* 96:20 4 */
> enum fs_context_purpose purpose:8; /* 152: 0 4 */
> enum fs_context_phase phase:8; /* 152: 8 4 */
> enum fs_value_type type:8; /* 8: 0 4 */
> enum sgx_page_type type:16; /* 8: 8 4 */
> enum nf_hook_ops_type hook_ops_type:8; /* 24: 8 4 */
> enum resctrl_event_id evtid:8; /* 0:10 4 */
> enum _cache_type type:5; /* 0: 0 4 */
next prev parent reply other threads:[~2023-09-06 23:20 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-03 3:25 [GIT PULL] bcachefs Kent Overstreet
2023-09-05 13:24 ` Christoph Hellwig
2023-09-06 0:00 ` Kent Overstreet
2023-09-06 0:41 ` Matthew Wilcox
2023-09-06 16:10 ` Kent Overstreet
2023-09-06 17:57 ` Darrick J. Wong
2023-09-08 9:37 ` Christoph Hellwig
2023-09-06 19:36 ` Linus Torvalds
2023-09-06 20:02 ` Linus Torvalds
2023-09-06 20:20 ` Linus Torvalds
2023-09-06 21:55 ` Arnaldo Carvalho de Melo
2023-09-06 23:13 ` David Sterba [this message]
2023-09-06 23:34 ` Linus Torvalds
2023-09-06 23:46 ` Arnaldo Carvalho de Melo
2023-09-06 23:53 ` Arnaldo Carvalho de Melo
2023-09-06 23:16 ` Linus Torvalds
2023-09-10 0:53 ` Kent Overstreet
2023-09-07 20:37 ` Kent Overstreet
2023-09-07 20:51 ` Linus Torvalds
2023-09-07 23:40 ` Kent Overstreet
2023-09-08 6:29 ` Martin Steigerwald
2023-09-08 9:11 ` Joshua Ashton
2023-09-06 22:28 ` Nathan Chancellor
2023-09-07 0:03 ` Kees Cook
2023-09-07 14:29 ` Chris Mason
2023-09-07 20:39 ` Kent Overstreet
2023-09-08 10:50 ` Brian Foster
2023-09-08 23:05 ` Dave Chinner
2023-09-08 10:59 ` Thank you! (was: Re: [GIT PULL] bcachefs) Martin Steigerwald
-- strict thread matches above, loose matches on Subject: below --
2023-06-26 21:46 [GIT PULL] bcachefs Kent Overstreet
2023-06-26 23:11 ` Jens Axboe
2023-06-27 0:06 ` Kent Overstreet
2023-06-27 1:13 ` Jens Axboe
2023-06-27 2:05 ` Kent Overstreet
2023-06-27 2:59 ` Jens Axboe
2023-06-27 3:10 ` Kent Overstreet
2023-06-27 17:16 ` Jens Axboe
2023-06-27 20:15 ` Kent Overstreet
2023-06-27 22:05 ` Dave Chinner
2023-06-27 22:41 ` Kent Overstreet
2023-06-28 14:40 ` Jens Axboe
2023-06-28 14:48 ` Thomas Weißschuh
2023-06-28 14:58 ` Jens Axboe
2023-06-28 3:16 ` Jens Axboe
2023-06-28 4:01 ` Kent Overstreet
2023-06-28 14:58 ` Jens Axboe
2023-06-28 15:22 ` Jens Axboe
2023-06-28 17:56 ` Kent Overstreet
2023-06-28 20:45 ` Jens Axboe
2023-06-28 16:57 ` Jens Axboe
2023-06-28 17:33 ` Christian Brauner
2023-06-28 17:52 ` Kent Overstreet
2023-06-28 20:44 ` Jens Axboe
2023-06-28 21:17 ` Jens Axboe
2023-06-28 22:13 ` Kent Overstreet
2023-06-28 22:33 ` Jens Axboe
2023-06-28 22:55 ` Kent Overstreet
2023-06-28 23:14 ` Jens Axboe
2023-06-28 23:50 ` Kent Overstreet
2023-06-29 1:00 ` Dave Chinner
2023-06-29 1:33 ` Jens Axboe
2023-06-29 11:18 ` Christian Brauner
2023-06-29 14:17 ` Kent Overstreet
2023-06-29 15:31 ` Kent Overstreet
2023-06-30 9:40 ` Christian Brauner
2023-07-06 15:20 ` Kent Overstreet
2023-07-06 16:26 ` Jens Axboe
2023-07-06 16:34 ` Kent Overstreet
2023-06-29 1:29 ` Jens Axboe
2023-07-06 20:15 ` Kent Overstreet
2023-06-28 17:54 ` Kent Overstreet
2023-06-28 20:54 ` Jens Axboe
2023-06-28 22:14 ` Jens Axboe
2023-06-28 23:04 ` Kent Overstreet
2023-06-28 23:11 ` Jens Axboe
2023-06-27 2:33 ` Kent Overstreet
2023-06-27 2:59 ` Jens Axboe
2023-06-27 3:19 ` Matthew Wilcox
2023-06-27 3:22 ` Kent Overstreet
2023-06-27 3:52 ` Christoph Hellwig
2023-06-27 4:36 ` Kent Overstreet
2023-07-06 15:56 ` Kent Overstreet
2023-07-06 16:40 ` Josef Bacik
2023-07-06 17:38 ` Kent Overstreet
2023-07-06 19:17 ` Eric Sandeen
2023-07-06 19:31 ` Kent Overstreet
2023-07-06 21:19 ` Darrick J. Wong
2023-07-06 22:43 ` Kent Overstreet
2023-07-07 13:13 ` Jan Kara
2023-07-07 13:52 ` Kent Overstreet
2023-07-07 8:48 ` Christian Brauner
2023-07-07 9:18 ` Kent Overstreet
2023-07-07 16:26 ` James Bottomley
2023-07-07 16:48 ` Kent Overstreet
2023-07-07 17:04 ` James Bottomley
2023-07-07 17:26 ` Kent Overstreet
2023-07-08 3:54 ` Matthew Wilcox
2023-07-08 4:10 ` Kent Overstreet
2023-07-08 4:31 ` Kent Overstreet
2023-07-08 15:02 ` Theodore Ts'o
2023-07-08 15:23 ` Kent Overstreet
2023-07-08 16:42 ` James Bottomley
2023-07-09 1:16 ` Kent Overstreet
2023-07-07 9:35 ` Kent Overstreet
2023-07-07 2:04 ` Theodore Ts'o
2023-07-07 12:18 ` Brian Foster
2023-07-07 14:49 ` Kent Overstreet
2023-07-12 2:54 ` Kent Overstreet
2023-07-12 19:48 ` Kees Cook
2023-07-12 19:57 ` Kent Overstreet
2023-07-12 22:10 ` Darrick J. Wong
2023-07-12 23:57 ` Kent Overstreet
2023-08-09 1:27 ` Linus Torvalds
2023-08-10 15:54 ` Kent Overstreet
2023-08-10 16:40 ` Linus Torvalds
2023-08-10 18:02 ` Kent Overstreet
2023-08-10 18:09 ` Linus Torvalds
2023-08-10 17:52 ` Jan Kara
2023-08-11 2:47 ` Kent Overstreet
2023-08-11 8:10 ` Jan Kara
2023-08-11 8:13 ` Christian Brauner
2023-08-10 22:39 ` Darrick J. Wong
2023-08-10 23:47 ` Linus Torvalds
2023-08-11 2:40 ` Jens Axboe
2023-08-11 4:03 ` Kent Overstreet
2023-08-11 5:20 ` Linus Torvalds
2023-08-11 5:29 ` Kent Overstreet
2023-08-11 5:53 ` Linus Torvalds
2023-08-11 7:52 ` Christian Brauner
2023-08-11 14:31 ` Jens Axboe
2023-08-11 3:45 ` Kent Overstreet
2023-08-21 0:09 ` Dave Chinner
2023-08-10 23:07 ` Matthew Wilcox
2023-08-11 10:54 ` Christian Brauner
2023-08-11 12:58 ` Kent Overstreet
2023-08-14 7:25 ` Christian Brauner
2023-08-14 15:23 ` Kent Overstreet
2023-08-11 13:21 ` Kent Overstreet
2023-08-11 22:56 ` Darrick J. Wong
2023-08-14 7:21 ` Christian Brauner
2023-08-14 15:27 ` Kent Overstreet
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