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Subject[PATCH 1/1] net/rds: Track user mapped pages through special API
Date
From: Leon Romanovsky <leonro@mellanox.com>

Convert net/rds to use the newly introduces pin_user_pages() API,
which properly sets FOLL_PIN. Setting FOLL_PIN is now required for
code that requires tracking of pinned pages.

Note that this effectively changes the code's behavior: it now
ultimately calls set_page_dirty_lock(), instead of set_page_dirty().
This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Cc: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Cc: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
net/rds/rdma.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 3341eee87bf9..585e6b3b69ce 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -162,10 +162,9 @@ static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,
if (write)
gup_flags |= FOLL_WRITE;

- ret = get_user_pages_fast(user_addr, nr_pages, gup_flags, pages);
+ ret = pin_user_pages_fast(user_addr, nr_pages, gup_flags, pages);
if (ret >= 0 && ret < nr_pages) {
- while (ret--)
- put_page(pages[ret]);
+ unpin_user_pages(pages, ret);
ret = -EFAULT;
}

@@ -300,8 +299,7 @@ static int __rds_rdma_map(struct rds_sock *rs, struct rds_get_mr_args *args,
* to release anything.
*/
if (!need_odp) {
- for (i = 0 ; i < nents; i++)
- put_page(sg_page(&sg[i]));
+ unpin_user_pages(pages, nr_pages);
kfree(sg);
}
ret = PTR_ERR(trans_private);
@@ -325,7 +323,12 @@ static int __rds_rdma_map(struct rds_sock *rs, struct rds_get_mr_args *args,
if (cookie_ret)
*cookie_ret = cookie;

- if (args->cookie_addr && put_user(cookie, (u64 __user *)(unsigned long) args->cookie_addr)) {
+ if (args->cookie_addr &&
+ put_user(cookie, (u64 __user *)(unsigned long)args->cookie_addr)) {
+ if (!need_odp) {
+ unpin_user_pages(pages, nr_pages);
+ kfree(sg);
+ }
ret = -EFAULT;
goto out;
}
@@ -496,9 +499,7 @@ void rds_rdma_free_op(struct rm_rdma_op *ro)
* is the case for a RDMA_READ which copies from remote
* to local memory
*/
- if (!ro->op_write)
- set_page_dirty(page);
- put_page(page);
+ unpin_user_pages_dirty_lock(&page, 1, !ro->op_write);
}
}

@@ -515,8 +516,7 @@ void rds_atomic_free_op(struct rm_atomic_op *ao)
/* Mark page dirty if it was possibly modified, which
* is the case for a RDMA_READ which copies from remote
* to local memory */
- set_page_dirty(page);
- put_page(page);
+ unpin_user_pages_dirty_lock(&page, 1, true);

kfree(ao->op_notifier);
ao->op_notifier = NULL;
@@ -944,7 +944,7 @@ int rds_cmsg_atomic(struct rds_sock *rs, struct rds_message *rm,
return ret;
err:
if (page)
- put_page(page);
+ unpin_user_page(page);
rm->atomic.op_active = 0;
kfree(rm->atomic.op_notifier);

--
2.25.0
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