* [PATCH] ata-sff: always map page before data transfer
@ 2017-05-02 16:29 Tycho Andersen
2017-05-04 9:51 ` Christoph Hellwig
0 siblings, 1 reply; 3+ messages in thread
From: Tycho Andersen @ 2017-05-02 16:29 UTC (permalink / raw)
To: Tejun Heo, Juerg Haefliger
Cc: linux-ide, linux-kernel, kernel-hardening, 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.
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Juerg Haefliger <juerg.haefliger@hpe.com>
CC: Tejun Heo <tj@kernel.org>
[1]: https://lkml.org/lkml/2016/11/4/245
[2]: https://lkml.org/lkml/2016/11/4/253
---
I don't understand all the factors at play here, so thoughts are definitely
welcome.
---
drivers/ata/libata-sff.c | 50 +++++++++++++++++-------------------------------
1 file changed, 18 insertions(+), 32 deletions(-)
diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 2bd92dc..8da2572 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -703,6 +703,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
struct page *page;
unsigned int offset;
unsigned char *buf;
+ unsigned long flags;
if (qc->curbytes == qc->nbytes - qc->sect_size)
ap->hsm_task_state = HSM_ST_LAST;
@@ -716,24 +717,16 @@ 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);
+ /* 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);
+ /* 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);
- }
+ kunmap_atomic(buf);
+ local_irq_restore(flags);
if (!do_write && !PageSlab(page))
flush_dcache_page(page);
@@ -836,6 +829,7 @@ static int __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
struct page *page;
unsigned char *buf;
unsigned int offset, count, consumed;
+ unsigned long flags;
next_sg:
sg = qc->cursg;
@@ -861,24 +855,16 @@ 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);
+ /* 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);
+ /* 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);
- }
+ kunmap_atomic(buf);
+ local_irq_restore(flags);
bytes -= min(bytes, consumed);
qc->curbytes += count;
--
2.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] ata-sff: always map page before data transfer
2017-05-02 16:29 [PATCH] ata-sff: always map page before data transfer Tycho Andersen
@ 2017-05-04 9:51 ` Christoph Hellwig
2017-05-04 22:18 ` Tycho Andersen
0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2017-05-04 9:51 UTC (permalink / raw)
To: Tycho Andersen
Cc: Tejun Heo, Juerg Haefliger, linux-ide, linux-kernel, kernel-hardening
> I don't understand all the factors at play here, so thoughts are definitely
> welcome.
I don't fully understand the old code either. One thing that is weird
is the "use a bounce buffer comment" which doesn't make any sense.
The other is the local_irq_save, which isn't really needed for
kmap_atomic to start with, but maybe that's the reason why the original
author didn't want to do it unconditionally?
So based on that:
> + /* FIXME: use a bounce buffer */
drop this comment..
> + local_irq_save(flags);
.. remove the local_irq_save/local_irq_restore ..
> + /* do the actual data transfer */
> + ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size,
> + do_write);
.. and a nice alittle cleanup move the do_write onto the previous line.
> + /* 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);
And same here.
And we should be fine.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] ata-sff: always map page before data transfer
2017-05-04 9:51 ` Christoph Hellwig
@ 2017-05-04 22:18 ` Tycho Andersen
0 siblings, 0 replies; 3+ messages in thread
From: Tycho Andersen @ 2017-05-04 22:18 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Tejun Heo, Juerg Haefliger, linux-ide, linux-kernel, kernel-hardening
On Thu, May 04, 2017 at 02:51:34AM -0700, Christoph Hellwig wrote:
> And we should be fine.
Great, I just sent a v2. Thanks!
Tycho
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-05-02 16:29 [PATCH] ata-sff: always map page before data transfer Tycho Andersen
2017-05-04 9:51 ` Christoph Hellwig
2017-05-04 22:18 ` Tycho Andersen
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