linux-kernel - [PATCH] staging: kpc2000: kpc_dma: Convert get_user_pages() --> pin_user

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Message-Id: <1590947491-11194-1-git-send-email-jrdr.linux@gmail.com>
Date:   Sun, 31 May 2020 23:21:31 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     gregkh@...uxfoundation.org, jane.pnx9@...il.com, simon@...anor.nu,
        harshjain32@...il.com, linux.bhar@...il.com, festevam@...il.com,
        jeremy@...zel.net
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Souptick Joarder <jrdr.linux@...il.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH] staging: kpc2000: kpc_dma: Convert get_user_pages() --> pin_user_pages()

In 2019, we introduced pin_user_pages*() and now we are converting
get_user_pages*() to the new API as appropriate. [1] & [2] could
be referred for more information.

When pin_user_pages() returns numbers of partially mapped pages,
those pages were not unpinned as part of error handling. Fixed
it as part of this patch.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
        https://lwn.net/Articles/807108/

Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
Cc: John Hubbard <jhubbard@...dia.com>
---
Hi,

I'm compile tested this, but unable to run-time test, so any testing
help is much appriciated.

 drivers/staging/kpc2000/kpc_dma/fileops.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c
index 8975346..29bab13 100644
--- a/drivers/staging/kpc2000/kpc_dma/fileops.c
+++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
@@ -48,6 +48,7 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 	u64 card_addr;
 	u64 dma_addr;
 	u64 user_ctl;
+	int nr_pages = 0;
 
 	ldev = priv->ldev;
 
@@ -76,13 +77,15 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 
 	// Lock the user buffer pages in memory, and hold on to the page pointers (for the sglist)
 	mmap_read_lock(current->mm);      /*  get memory map semaphore */
-	rv = get_user_pages(iov_base, acd->page_count, FOLL_TOUCH | FOLL_WRITE | FOLL_GET, acd->user_pages, NULL);
+	rv = pin_user_pages(iov_base, acd->page_count, FOLL_TOUCH | FOLL_WRITE, acd->user_pages, NULL);
 	mmap_read_unlock(current->mm);        /*  release the semaphore */
 	if (rv != acd->page_count) {
-		dev_err(&priv->ldev->pldev->dev, "Couldn't get_user_pages (%ld)\n", rv);
+		dev_err(&priv->ldev->pldev->dev, "Couldn't pin_user_pages (%ld)\n", rv);
+		nr_pages = rv;
 		goto err_get_user_pages;
 	}
 
+	nr_pages = acd->page_count;
 	// Allocate and setup the sg_table (scatterlist entries)
 	rv = sg_alloc_table_from_pages(&acd->sgt, acd->user_pages, acd->page_count, iov_base & (PAGE_SIZE - 1), iov_len, GFP_KERNEL);
 	if (rv) {
@@ -189,10 +192,9 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 	sg_free_table(&acd->sgt);
  err_dma_map_sg:
  err_alloc_sg_table:
-	for (i = 0 ; i < acd->page_count ; i++)
-		put_page(acd->user_pages[i]);
-
  err_get_user_pages:
+	if (nr_pages > 0)
+		unpin_user_pages(acd->user_pages, nr_pages);
 	kfree(acd->user_pages);
  err_alloc_userpages:
 	kfree(acd);
@@ -217,8 +219,7 @@ void  transfer_complete_cb(struct aio_cb_data *acd, size_t xfr_count, u32 flags)
 
 	dma_unmap_sg(&acd->ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, acd->ldev->dir);
 
-	for (i = 0 ; i < acd->page_count ; i++)
-		put_page(acd->user_pages[i]);
+	unpin_user_pages(acd->user_pages, acd->page_count);
 
 	sg_free_table(&acd->sgt);
 
-- 
1.9.1