From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
"Darrick J. Wong" <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>, Matthew Wilcox <willy@infradead.org>,
cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com,
Andreas Gruenbacher <agruenba@redhat.com>
Subject: [PATCH v3 6/7] iov_iter: Introduce noio flag to disable page faults
Date: Fri, 23 Jul 2021 22:58:39 +0200 [thread overview]
Message-ID: <20210723205840.299280-7-agruenba@redhat.com> (raw)
In-Reply-To: <20210723205840.299280-1-agruenba@redhat.com>
Introduce a new noio flag to indicate to get_user_pages to use the
FOLL_FAST_ONLY flag. This will cause get_user_pages to fail when it
would otherwise fault in a page.
Currently, the noio flag is only checked in iov_iter_get_pages and
iov_iter_get_pages_alloc. This is enough for iomaop_dio_rw, but it
may make sense to check for this flag in other contexts as well.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
include/linux/uio.h | 1 +
lib/iov_iter.c | 20 +++++++++++++++-----
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 152b3605e86c..8de6354ade14 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -29,6 +29,7 @@ enum iter_type {
struct iov_iter {
u8 iter_type;
+ bool noio;
bool data_source;
size_t iov_offset;
size_t count;
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7221665f7ac4..a20426cedf60 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -509,6 +509,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter) {
.iter_type = ITER_IOVEC,
+ .noio = false,
.data_source = direction,
.iov = iov,
.nr_segs = nr_segs,
@@ -1519,13 +1520,17 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
return 0;
if (likely(iter_is_iovec(i))) {
+ unsigned int gup_flags = 0;
unsigned long addr;
+ if (iov_iter_rw(i) != WRITE)
+ gup_flags |= FOLL_WRITE;
+ if (i->noio)
+ gup_flags |= FOLL_FAST_ONLY;
+
addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
n = DIV_ROUND_UP(len, PAGE_SIZE);
- res = get_user_pages_fast(addr, n,
- iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0,
- pages);
+ res = get_user_pages_fast(addr, n, gup_flags, pages);
if (unlikely(res <= 0))
return res;
return (res == n ? len : res * PAGE_SIZE) - *start;
@@ -1641,15 +1646,20 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
return 0;
if (likely(iter_is_iovec(i))) {
+ unsigned int gup_flags = 0;
unsigned long addr;
+ if (iov_iter_rw(i) != WRITE)
+ gup_flags |= FOLL_WRITE;
+ if (i->noio)
+ gup_flags |= FOLL_FAST_ONLY;
+
addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
n = DIV_ROUND_UP(len, PAGE_SIZE);
p = get_pages_array(n);
if (!p)
return -ENOMEM;
- res = get_user_pages_fast(addr, n,
- iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0, p);
+ res = get_user_pages_fast(addr, n, gup_flags, p);
if (unlikely(res <= 0)) {
kvfree(p);
*pages = ZERO_SIZE_PTR;
--
2.26.3
next prev parent reply other threads:[~2021-07-23 20:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 20:58 [PATCH v3 0/7] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 1/7] iov_iter: Introduce fault_in_iov_iter helper Andreas Gruenbacher
2021-07-23 23:40 ` Linus Torvalds
2021-07-24 7:51 ` Andreas Grünbacher
2021-07-24 1:52 ` Al Viro
2021-07-24 8:05 ` Andreas Grünbacher
2021-07-26 16:33 ` Jan Kara
2021-07-26 17:15 ` Linus Torvalds
2021-07-23 20:58 ` [PATCH v3 2/7] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 3/7] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 4/7] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 5/7] iomap: Support restarting direct I/O requests after user copy failures Andreas Gruenbacher
2021-07-26 17:19 ` Jan Kara
[not found] ` <CAHpGcMLtQ1=WOT1mTUS4=iWBwHLQ-EBzY=+XuSGJfu4gVPYTLw@mail.gmail.com>
2021-07-26 18:08 ` Jan Kara
2021-07-23 20:58 ` Andreas Gruenbacher [this message]
2021-07-23 20:58 ` [PATCH v3 7/7] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher
2021-07-26 17:02 ` Jan Kara
[not found] ` <CAHpGcMLOZhZ7tGrY7rcYWUwx12sY884T=eC-Ckna63PBmF=zwA@mail.gmail.com>
2021-07-26 18:00 ` Jan Kara
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