From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
David Sterba <dsterba@suse.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Anton Altaparmakov <anton@tuxera.com>,
David Howells <dhowells@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Pavel Begunkov <asml.silence@gmail.com>
Subject: [RFC PATCH 01/37] ntfs_copy_from_user_iter(): don't bother with copying iov_iter
Date: Sun, 6 Jun 2021 19:10:15 +0000 [thread overview]
Message-ID: <20210606191051.1216821-1-viro@zeniv.linux.org.uk> (raw)
In-Reply-To: <YL0dCEVEiVL+NwG6@zeniv-ca.linux.org.uk>
Advance the original, let the caller revert if it needs to.
Don't mess with iov_iter_single_seg_count() in the caller -
if we got a (non-zero) short copy, use the amount actually
copied for the next pass, limit it to "up to the end
of page" if nothing got copied at all.
Originally fault-in only read the first iovec; back then it used
to make sense to limit to the just one iovec for the pass after
short copy. These days it's no long true.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/ntfs/file.c | 33 +++++++++++----------------------
1 file changed, 11 insertions(+), 22 deletions(-)
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index e5aab265dff1..0666d4578137 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1684,20 +1684,19 @@ static size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
{
struct page **last_page = pages + nr_pages;
size_t total = 0;
- struct iov_iter data = *i;
unsigned len, copied;
do {
len = PAGE_SIZE - ofs;
if (len > bytes)
len = bytes;
- copied = iov_iter_copy_from_user_atomic(*pages, &data, ofs,
+ copied = iov_iter_copy_from_user_atomic(*pages, i, ofs,
len);
+ iov_iter_advance(i, copied);
total += copied;
bytes -= copied;
if (!bytes)
break;
- iov_iter_advance(&data, copied);
if (copied < len)
goto err;
ofs = 0;
@@ -1866,34 +1865,24 @@ static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
if (likely(copied == bytes)) {
status = ntfs_commit_pages_after_write(pages, do_pages,
pos, bytes);
- if (!status)
- status = bytes;
}
do {
unlock_page(pages[--do_pages]);
put_page(pages[do_pages]);
} while (do_pages);
- if (unlikely(status < 0))
+ if (unlikely(status < 0)) {
+ iov_iter_revert(i, copied);
break;
- copied = status;
+ }
cond_resched();
- if (unlikely(!copied)) {
- size_t sc;
-
- /*
- * We failed to copy anything. Fall back to single
- * segment length write.
- *
- * This is needed to avoid possible livelock in the
- * case that all segments in the iov cannot be copied
- * at once without a pagefault.
- */
- sc = iov_iter_single_seg_count(i);
- if (bytes > sc)
- bytes = sc;
+ if (unlikely(copied < bytes)) {
+ iov_iter_revert(i, copied);
+ if (copied)
+ bytes = copied;
+ else if (bytes > PAGE_SIZE - ofs)
+ bytes = PAGE_SIZE - ofs;
goto again;
}
- iov_iter_advance(i, copied);
pos += copied;
written += copied;
balance_dirty_pages_ratelimited(mapping);
--
2.11.0
next prev parent reply other threads:[~2021-06-06 19:11 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-06 19:07 [RFC][PATCHSET] iov_iter work Al Viro
2021-06-06 19:10 ` Al Viro [this message]
2021-06-06 19:10 ` [RFC PATCH 02/37] generic_perform_write()/iomap_write_actor(): saner logics for short copy Al Viro
2021-06-06 19:10 ` [RFC PATCH 03/37] fuse_fill_write_pages(): don't bother with iov_iter_single_seg_count() Al Viro
2021-06-06 19:10 ` [RFC PATCH 04/37] iov_iter: Remove iov_iter_for_each_range() Al Viro
2021-06-06 19:10 ` [RFC PATCH 05/37] teach copy_page_to_iter() to handle compound pages Al Viro
2021-06-06 19:10 ` [RFC PATCH 06/37] copy_page_to_iter(): fix ITER_DISCARD case Al Viro
2021-06-06 19:10 ` [RFC PATCH 07/37] [xarray] iov_iter_fault_in_readable() should do nothing in xarray case Al Viro
2021-06-06 19:10 ` [RFC PATCH 08/37] iov_iter_advance(): use consistent semantics for move past the end Al Viro
2021-06-06 19:10 ` [RFC PATCH 09/37] iov_iter: switch ..._full() variants of primitives to use of iov_iter_revert() Al Viro
2021-06-06 19:10 ` [RFC PATCH 10/37] iov_iter: reorder handling of flavours in primitives Al Viro
2021-06-06 19:10 ` [RFC PATCH 11/37] iov_iter_advance(): don't modify ->iov_offset for ITER_DISCARD Al Viro
2021-06-06 19:10 ` [RFC PATCH 12/37] iov_iter: separate direction from flavour Al Viro
2021-06-06 19:10 ` [RFC PATCH 13/37] iov_iter: optimize iov_iter_advance() for iovec and kvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 14/37] sanitize iov_iter_fault_in_readable() Al Viro
2021-06-06 19:10 ` [RFC PATCH 15/37] iov_iter_alignment(): don't bother with iterate_all_kinds() Al Viro
2021-06-06 19:10 ` [RFC PATCH 16/37] iov_iter_gap_alignment(): get rid of iterate_all_kinds() Al Viro
2021-06-09 13:01 ` Qian Cai
2021-06-09 18:06 ` Al Viro
2021-06-06 19:10 ` [RFC PATCH 17/37] get rid of iterate_all_kinds() in iov_iter_get_pages()/iov_iter_get_pages_alloc() Al Viro
2021-06-06 19:10 ` [RFC PATCH 18/37] iov_iter_npages(): don't bother with iterate_all_kinds() Al Viro
2021-06-06 19:10 ` [RFC PATCH 19/37] [xarray] iov_iter_npages(): just use DIV_ROUND_UP() Al Viro
2021-06-06 19:10 ` [RFC PATCH 20/37] iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant Al Viro
2021-06-06 19:10 ` [RFC PATCH 21/37] csum_and_copy_to_iter(): massage into form closer to csum_and_copy_from_iter() Al Viro
2021-06-06 19:10 ` [RFC PATCH 22/37] iterate_and_advance(): get rid of magic in case when n is 0 Al Viro
2021-06-06 19:10 ` [RFC PATCH 23/37] iov_iter: massage iterate_iovec and iterate_kvec to logics similar to iterate_bvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 24/37] iov_iter: unify iterate_iovec and iterate_kvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 25/37] iterate_bvec(): expand bvec.h macro forest, massage a bit Al Viro
2021-06-06 19:10 ` [RFC PATCH 26/37] iov_iter: teach iterate_{bvec,xarray}() about possible short copies Al Viro
2021-06-06 19:10 ` [RFC PATCH 27/37] iov_iter: get rid of separate bvec and xarray callbacks Al Viro
2021-06-06 19:10 ` [RFC PATCH 28/37] iov_iter: make the amount already copied available to iterator callbacks Al Viro
2021-06-06 19:10 ` [RFC PATCH 29/37] iov_iter: make iterator callbacks use base and len instead of iovec Al Viro
2021-06-06 19:10 ` [RFC PATCH 30/37] pull handling of ->iov_offset into iterate_{iovec,bvec,xarray} Al Viro
2021-06-06 19:10 ` [RFC PATCH 31/37] iterate_xarray(): only of the first iteration we might get offset != 0 Al Viro
2021-06-06 19:10 ` [RFC PATCH 32/37] copy_page_to_iter(): don't bother with kmap_atomic() for bvec/kvec cases Al Viro
2021-06-06 19:10 ` [RFC PATCH 33/37] copy_page_from_iter(): don't need kmap_atomic() for kvec/bvec cases Al Viro
2021-06-06 19:10 ` [RFC PATCH 34/37] iov_iter: clean csum_and_copy_...() primitives up a bit Al Viro
2021-06-06 19:10 ` [RFC PATCH 35/37] pipe_zero(): we don't need no stinkin' kmap_atomic() Al Viro
2021-06-06 19:10 ` [RFC PATCH 36/37] clean up copy_mc_pipe_to_iter() Al Viro
2021-06-06 19:10 ` [RFC PATCH 37/37] csum_and_copy_to_pipe_iter(): leave handling of csum_state to caller Al Viro
2021-06-06 22:05 ` [RFC][PATCHSET] iov_iter work Linus Torvalds
2021-06-06 22:46 ` Linus Torvalds
2021-06-07 9:28 ` Christoph Hellwig
2021-06-07 14:43 ` Al Viro
2021-06-07 15:59 ` Christoph Hellwig
2021-06-07 21:07 ` Al Viro
2021-06-07 22:01 ` Linus Torvalds
2021-06-07 23:35 ` Linus Torvalds
2021-06-08 5:25 ` Christoph Hellwig
2021-06-08 11:27 ` Al Viro
2021-06-06 23:29 ` Al Viro
2021-06-07 10:38 ` Pavel Begunkov
2021-06-08 14:43 ` David Laight
2021-06-10 14:29 ` Qian Cai
2021-06-10 15:35 ` Al Viro
2021-06-10 15:48 ` Al Viro
2021-06-10 19:08 ` Qian Cai
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