[PATCH v2] ata-sff: always map page before data transfer

[Tycho Andersen]

The XPFO [1] patchset may unmap pages from physmap if they happened to be
destined for userspace. If such a page is unmapped, it needs to be
remapped. Rather than test if a page is in the highmem/xpfo unmapped state,
Christoph suggested [2] that we simply always map the page.

v2: * drop comment about bounce buffer
    * don't save IRQs before kmap/unmap
    * formatting

Suggested-by: Christoph Hellwig <h...@infradead.org>
Signed-off-by: Tycho Andersen <ty...@docker.com>
CC: Juerg Haefliger <juerg.haefli...@hpe.com>
CC: Tejun Heo <t...@kernel.org>

[1]: https://lkml.org/lkml/2016/11/4/245
[2]: https://lkml.org/lkml/2016/11/4/253
---
v1: https://lkml.org/lkml/2017/5/2/404
---
 drivers/ata/libata-sff.c | 44 ++++++++------------------------------------
 1 file changed, 8 insertions(+), 36 deletions(-)

diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 2bd92dca3e62..01cf07c919bc 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -716,24 +716,10 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
 
        DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");
 
-       if (PageHighMem(page)) {
-               unsigned long flags;
-
-               /* FIXME: use a bounce buffer */
-               local_irq_save(flags);
-               buf = kmap_atomic(page);
-
-               /* do the actual data transfer */
-               ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size,
-                                      do_write);
-
-               kunmap_atomic(buf);
-               local_irq_restore(flags);
-       } else {
-               buf = page_address(page);
-               ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size,
-                                      do_write);
-       }
+       /* do the actual data transfer */
+       buf = kmap_atomic(page);
+       ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size, do_write);
+       kunmap_atomic(buf);
 
        if (!do_write && !PageSlab(page))
                flush_dcache_page(page);
@@ -861,24 +847,10 @@ static int __atapi_pio_bytes(struct ata_queued_cmd *qc, 
unsigned int bytes)
 
        DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");
 
-       if (PageHighMem(page)) {
-               unsigned long flags;
-
-               /* FIXME: use bounce buffer */
-               local_irq_save(flags);
-               buf = kmap_atomic(page);
-
-               /* do the actual data transfer */
-               consumed = ap->ops->sff_data_xfer(qc, buf + offset,
-                                                               count, rw);
-
-               kunmap_atomic(buf);
-               local_irq_restore(flags);
-       } else {
-               buf = page_address(page);
-               consumed = ap->ops->sff_data_xfer(qc, buf + offset,
-                                                               count, rw);
-       }
+       /* do the actual data transfer */
+       buf = kmap_atomic(page);
+       consumed = ap->ops->sff_data_xfer(qc, buf + offset, count, rw);
+       kunmap_atomic(buf);
 
        bytes -= min(bytes, consumed);
        qc->curbytes += count;
-- 
2.11.0