From 08e9cbe75facfe08b9017eca37c9f1c5a6490b4a Mon Sep 17 00:00:00 2001 From: John Hubbard Date: Tue, 26 May 2020 11:27:09 -0700 Subject: scsi: st: Convert convert get_user_pages() --> pin_user_pages() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This code was using get_user_pages*(), in a "Case 1" scenario (Direct IO), using the categorization from [1]. That means that it's time to convert the get_user_pages*() + put_page() calls to pin_user_pages*() + unpin_user_pages() calls. There is some helpful background in [2]: basically, this is a small part of fixing a long-standing disconnect between pinning pages, and file systems' use of those pages. Note that this effectively changes the code's behavior as well: it now ultimately calls set_page_dirty_lock(), instead of SetPageDirty().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." [3] Also, this deletes one of the two FIXME comments (about refcounting), because there is nothing wrong with the refcounting at this point. [1] Documentation/core-api/pin_user_pages.rst [2] "Explicit pinning of user-space pages": https://lwn.net/Articles/807108/ [3] https://lore.kernel.org/r/20190723153640.GB720@lst.de Link: https://lore.kernel.org/r/20200526182709.99599-1-jhubbard@nvidia.com Cc: "Kai Mäkisara (Kolumbus)" Cc: Bart Van Assche Cc: James E.J. Bottomley Cc: Martin K. Petersen Cc: linux-scsi@vger.kernel.org Acked-by: Kai Mäkisara Signed-off-by: John Hubbard Signed-off-by: Martin K. Petersen --- drivers/scsi/st.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) (limited to 'drivers/scsi/st.c') diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index 4bf4ab3b70f4..87fbc0ea350b 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -4921,7 +4921,7 @@ static int sgl_map_user_pages(struct st_buffer *STbp, unsigned long end = (uaddr + count + PAGE_SIZE - 1) >> PAGE_SHIFT; unsigned long start = uaddr >> PAGE_SHIFT; const int nr_pages = end - start; - int res, i, j; + int res, i; struct page **pages; struct rq_map_data *mdata = &STbp->map_data; @@ -4943,7 +4943,7 @@ static int sgl_map_user_pages(struct st_buffer *STbp, /* Try to fault in all of the necessary pages */ /* rw==READ means read from drive, write into memory area */ - res = get_user_pages_fast(uaddr, nr_pages, rw == READ ? FOLL_WRITE : 0, + res = pin_user_pages_fast(uaddr, nr_pages, rw == READ ? FOLL_WRITE : 0, pages); /* Errors and no page mapped should return here */ @@ -4963,8 +4963,7 @@ static int sgl_map_user_pages(struct st_buffer *STbp, return nr_pages; out_unmap: if (res > 0) { - for (j=0; j < res; j++) - put_page(pages[j]); + unpin_user_pages(pages, res); res = 0; } kfree(pages); @@ -4976,18 +4975,9 @@ static int sgl_map_user_pages(struct st_buffer *STbp, static int sgl_unmap_user_pages(struct st_buffer *STbp, const unsigned int nr_pages, int dirtied) { - int i; - - for (i=0; i < nr_pages; i++) { - struct page *page = STbp->mapped_pages[i]; + /* FIXME: cache flush missing for rw==READ */ + unpin_user_pages_dirty_lock(STbp->mapped_pages, nr_pages, dirtied); - if (dirtied) - SetPageDirty(page); - /* FIXME: cache flush missing for rw==READ - * FIXME: call the correct reference counting function - */ - put_page(page); - } kfree(STbp->mapped_pages); STbp->mapped_pages = NULL; -- cgit v1.2.3