From: Linus Torvalds <torvalds@linux-foundation.org>
To: Omar Sandoval <osandov@osandov.com>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Linux API <linux-api@vger.kernel.org>,
Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH RESEND x3 v9 1/9] iov_iter: add copy_struct_from_iter()
Date: Fri, 18 Jun 2021 11:50:25 -0700 [thread overview]
Message-ID: <CAHk-=whRA=54dtO3ha-C2-fV4XQ2nry99BmfancW-16EFGTHVg@mail.gmail.com> (raw)
In-Reply-To: <6caae597eb20da5ea23e53e8e64ce0c4f4d9c6d2.1623972519.git.osandov@fb.com>
On Thu, Jun 17, 2021 at 4:51 PM Omar Sandoval <osandov@osandov.com> wrote:
>
> This is essentially copy_struct_from_user() but for an iov_iter.
So I continue to think that this series looks fine - if we want this
interface at all.
I do note a few issues with this iov patch, though - partly probably
because I have been reading Al's cleanup patches that had some
optimizations in place.
And in particular, I now react to this:
> + iov_iter_advance(i, usize);
at the end of copy_struct_from_iter().
It's very wasteful to use the generic iov_iter_advance() function,
when you just had special functions for each of the iterator cases.
Because that generic function will now just end up re-testing that
whole "what kind was it" and then do each kind separately.
So it would actually be a lot simpler and m,ore efficient to just do
that "advance" part as you go through the cases, iow just do
iov_iter_iovec_advance(i, usize);
at the end of the iter_is_iovec/iter_is_kvec cases, and
iov_iter_bvec_advance(i, usize)
for the bvec case.
I think that you may need it to be based on Al's series for that to
work, which might be inconvenient, though.
One other non-code issue: particularly since you only handle a subset
of the iov_iter cases, it would be nice to have an explanation for
_why_ those particular cases.
IOW, have some trivial explanation for each of the cases. "iovec" is
for regular read/write, what triggers the kvec and bvec cases?
But also, the other way around. Why doesn't the pipe case trigger? No
splice support?
Linus
next prev parent reply other threads:[~2021-06-18 18:50 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 23:51 [PATCH RESEND x3 v9 0/9] fs: interface for directly reading/writing compressed data Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 1/9] iov_iter: add copy_struct_from_iter() Omar Sandoval
2021-06-18 18:50 ` Linus Torvalds [this message]
2021-06-18 19:42 ` Al Viro
2021-06-18 19:49 ` Al Viro
2021-06-18 20:33 ` Omar Sandoval
2021-06-18 20:32 ` Omar Sandoval
2021-06-18 20:58 ` Al Viro
2021-06-18 21:10 ` Linus Torvalds
2021-06-18 21:32 ` Al Viro
2021-06-18 21:40 ` Linus Torvalds
2021-06-18 22:10 ` Omar Sandoval
2021-06-18 22:32 ` Al Viro
2021-06-19 0:43 ` Omar Sandoval
2021-06-21 18:46 ` Omar Sandoval
2021-06-21 19:33 ` Linus Torvalds
2021-06-21 20:46 ` Omar Sandoval
2021-06-21 20:53 ` Omar Sandoval
2021-06-21 20:55 ` Omar Sandoval
2021-06-22 22:06 ` Dave Chinner
2021-06-23 17:49 ` Omar Sandoval
2021-06-23 18:28 ` Linus Torvalds
2021-06-23 19:33 ` Omar Sandoval
2021-06-23 19:45 ` Al Viro
2021-06-23 20:46 ` Omar Sandoval
2021-06-23 21:39 ` Al Viro
2021-06-23 21:58 ` Omar Sandoval
2021-06-23 22:26 ` Al Viro
2021-06-24 2:00 ` Matthew Wilcox
2021-06-24 6:14 ` Omar Sandoval
2021-06-24 17:52 ` Linus Torvalds
2021-06-24 18:28 ` Omar Sandoval
2021-06-24 21:07 ` Linus Torvalds
2021-06-24 22:41 ` Martin K. Petersen
2021-06-25 3:38 ` Matthew Wilcox
2021-06-25 16:16 ` Linus Torvalds
2021-06-25 21:07 ` Omar Sandoval
2021-07-07 17:59 ` Omar Sandoval
2021-07-19 15:44 ` Josef Bacik
2021-06-24 6:41 ` Christoph Hellwig
2021-06-24 7:50 ` Omar Sandoval
2021-06-18 22:14 ` Al Viro
2021-06-17 23:51 ` [PATCH RESEND x3 v9 2/9] fs: add O_ALLOW_ENCODED open flag Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 3/9] fs: add RWF_ENCODED for reading/writing compressed data Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 4/9] btrfs: don't advance offset for compressed bios in btrfs_csum_one_bio() Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 5/9] btrfs: add ram_bytes and offset to btrfs_ordered_extent Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 6/9] btrfs: support different disk extent size for delalloc Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 7/9] btrfs: optionally extend i_size in cow_file_range_inline() Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 8/9] btrfs: implement RWF_ENCODED reads Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 9/9] btrfs: implement RWF_ENCODED writes Omar Sandoval
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