fb_defio: do not use deprecated page->mapping, index fields

With the introduction of mapping_wrprotect_range() there is no need to use
folio_mkclean() in order to write-protect mappings of frame buf

fb_defio: do not use deprecated page->mapping, index fields

With the introduction of mapping_wrprotect_range() there is no need to use
folio_mkclean() in order to write-protect mappings of frame buffer pages,
and therefore no need to inappropriately set kernel-allocated page->index,
mapping fields to permit this operation.

Instead, store the pointer to the page cache object for the mapped driver
in the fb_deferred_io object, and use the already stored page offset from
the pageref object to look up mappings in order to write-protect them.

This is justified, as for the page objects to store a mapping pointer at
the point of assignment of pages, they must all reference the same
underlying address_space object. Since the life time of the pagerefs is
also the lifetime of the fb_deferred_io object, storing the pointer here
makes sense.

This eliminates the need for all of the logic around setting and
maintaining page->index,mapping which we remove.

This eliminates the use of folio_mkclean() entirely but otherwise should
have no functional change.

[[email protected]: fixup unused variable warnings]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/81171ab16c14e3df28f6de9d14982cee528d8519.1739029358.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <[email protected]>
Tested-by: Kajtar Zsolt <[email protected]>
Acked-by: Thomas Zimmermann <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Jaya Kumar <[email protected]>
Cc: Maíra Canal <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Simona Vetter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

show more ...

mm: remove page_mkclean()

There are no more users of page_mkclean(), remove it and update the
document and comment.

Link: https://lkml.kernel.org/r/[email protected]

mm: remove page_mkclean()

There are no more users of page_mkclean(), remove it and update the
document and comment.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kefeng Wang <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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fb_defio: use a folio in fb_deferred_io_work()

Replaces three calls to compound_head() with one, which removes last
caller of page_mkclean().

Link: https://lkml.kernel.org/r/20240604114822.2089819-

fb_defio: use a folio in fb_deferred_io_work()

Replaces three calls to compound_head() with one, which removes last
caller of page_mkclean().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kefeng Wang <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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fbdev/deferred-io: Provide get_page hook in struct fb_deferred_io

Add a callback for drivers to provide framebuffer pages to fbdev's
deferred-I/O helpers. Implementations need to acquire a reference

fbdev/deferred-io: Provide get_page hook in struct fb_deferred_io

Add a callback for drivers to provide framebuffer pages to fbdev's
deferred-I/O helpers. Implementations need to acquire a reference on
the page before returning it. Returning NULL generates a SIGBUS
signal.

This will be useful for DRM's fbdev emulation with GEM-shmem buffer
objects.

v2:
- fix typo in commit message (Javier)

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev/deferred-io: Always call get_page() for framebuffer pages

Unconditionally call get_page() after looking up a page from the
framebuffer memory. Guarantees that we always hold a reference.

This

fbdev/deferred-io: Always call get_page() for framebuffer pages

Unconditionally call get_page() after looking up a page from the
framebuffer memory. Guarantees that we always hold a reference.

This change also refactors the code such that it can support a
driver-supplied get_page helper. This will be useful for DRM's
fbdev emulation.

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev/deferred-io: Test smem_start for I/O memory

Test smem_start before looking up pages from its value. Return
NULL if it is unset. This will result in a SIGBUS signal.

Signed-off-by: Thomas Zimm

fbdev/deferred-io: Test smem_start for I/O memory

Test smem_start before looking up pages from its value. Return
NULL if it is unset. This will result in a SIGBUS signal.

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev/deferred-io: Test screen_buffer for vmalloc'ed memory

Framebuffers in virtual memory are available via screen_buffer. Use
it instead of screen_base and avoid the type casting.

Signed-off-by:

fbdev/deferred-io: Test screen_buffer for vmalloc'ed memory

Framebuffers in virtual memory are available via screen_buffer. Use
it instead of screen_base and avoid the type casting.

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev/deferred-io: Clean up pageref on lastclose

Clean up the pageref state as part of the lastclose helper. This
only requires to clear the page's mapping field. The pageref and
page can stay in pl

fbdev/deferred-io: Clean up pageref on lastclose

Clean up the pageref state as part of the lastclose helper. This
only requires to clear the page's mapping field. The pageref and
page can stay in place for the next opened instance of the frame-
buffer file.

With the change in the clean-up logic, there's no further need
to look up pages during the lastclose cleanup. The code instead
uses the existing pagerefs in its look-up table. It also avoids
using smem_len, which some driver might not set correctly.

v2:
- fix typos in commit message (Javier)

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev/deferred-io: Move pageref setup into separate helper

Set up struct fb_deferred_io_pageref in the new helper function
fb_deferred_io_pageref_lookup(), which runs when the pageref is first
taken

fbdev/deferred-io: Move pageref setup into separate helper

Set up struct fb_deferred_io_pageref in the new helper function
fb_deferred_io_pageref_lookup(), which runs when the pageref is first
taken. Remove the setup code from the rest of the code.

At first, the code allocates the memory of all pageref structs. The
setup of the various fields happens when the pageref is required.

v2:
- fix typo in commit message (Javier)

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: fix incorrect address computation in deferred IO

With deferred IO enabled, a page fault happens when data is written to the
framebuffer device. Then driver determines which page is being upda

fbdev: fix incorrect address computation in deferred IO

With deferred IO enabled, a page fault happens when data is written to the
framebuffer device. Then driver determines which page is being updated by
calculating the offset of the written virtual address within the virtual
memory area, and uses this offset to get the updated page within the
internal buffer. This page is later copied to hardware (thus the name
"deferred IO").

This offset calculation is only correct if the virtual memory area is
mapped to the beginning of the internal buffer. Otherwise this is wrong.
For example, if users do:
mmap(ptr, 4096, PROT_WRITE, MAP_FIXED | MAP_SHARED, fd, 0xff000);

Then the virtual memory area will mapped at offset 0xff000 within the
internal buffer. This offset 0xff000 is not accounted for, and wrong page
is updated.

Correct the calculation by using vmf->pgoff instead. With this change, the
variable "offset" will no longer hold the exact offset value, but it is
rounded down to multiples of PAGE_SIZE. But this is still correct, because
this variable is only used to calculate the page offset.

Reported-by: Harshit Mogalapalli <[email protected]>
Closes: https://lore.kernel.org/linux-fbdev/[email protected]
Fixes: 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct")
Cc: <[email protected]>
Signed-off-by: Nam Cao <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Tested-by: Harshit Mogalapalli <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: flush deferred IO before closing

When framebuffer gets closed, the queued deferred IO gets cancelled. This
can cause some last display data to vanish. This is problematic for users
who send a

fbdev: flush deferred IO before closing

When framebuffer gets closed, the queued deferred IO gets cancelled. This
can cause some last display data to vanish. This is problematic for users
who send a still image to the framebuffer, then close the file: the image
may never appear.

To ensure none of display data get lost, flush the queued deferred IO
first before closing.

Another possible solution is to delete the cancel_delayed_work_sync()
instead. The difference is that the display may appear some time after
closing. However, the clearing of page mapping after this needs to be
removed too, because the page mapping is used by the deferred work. It is
not completely obvious whether it is okay to not clear the page mapping.
For a patch intended for stable trees, go with the simple and obvious
solution.

Fixes: 60b59beafba8 ("fbdev: mm: Deferred IO support")
Cc: [email protected]
Signed-off-by: Nam Cao <[email protected]>
Reviewed-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Helge Deller <[email protected]>

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fbdev: flush deferred work in fb_deferred_io_fsync()

The driver's fsync() is supposed to flush any pending operation to
hardware. It is implemented in this driver by cancelling the queued
deferred I

fbdev: flush deferred work in fb_deferred_io_fsync()

The driver's fsync() is supposed to flush any pending operation to
hardware. It is implemented in this driver by cancelling the queued
deferred IO first, then schedule it for "immediate execution" by calling
schedule_delayed_work() again with delay=0. However, setting delay=0
only means the work is scheduled immediately, it does not mean the work
is executed immediately. There is no guarantee that the work is finished
after schedule_delayed_work() returns. After this driver's fsync()
returns, there can still be pending work. Furthermore, if close() is
called by users immediately after fsync(), the pending work gets
cancelled and fsync() may do nothing.

To ensure that the deferred IO completes, use flush_delayed_work()
instead. Write operations to this driver either write to the device
directly, or invoke schedule_delayed_work(); so by flushing the
workqueue, it can be guaranteed that all previous writes make it to the
device.

Fixes: 5e841b88d23d ("fb: fsync() method for deferred I/O flush.")
Cc: [email protected]
Signed-off-by: Nam Cao <[email protected]>
Reviewed-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Helge Deller <[email protected]>

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fbdev: Push pgprot_decrypted() into mmap implementations

If a driver sets struct fb_ops.fb_mmap, the fbdev core automatically
calls pgprot_decrypted(). But the default fb_mmap code doesn't handle
pg

fbdev: Push pgprot_decrypted() into mmap implementations

If a driver sets struct fb_ops.fb_mmap, the fbdev core automatically
calls pgprot_decrypted(). But the default fb_mmap code doesn't handle
pgprot_decrypted().

Move the call to pgprot_decrypted() into each drivers' fb_mmap function.
This only concerns fb_mmap functions for system and DMA memory. For
I/O memory, which is the default case, nothing changes. The fb_mmap
for I/O-memory can later be moved into a helper as well.

DRM's fbdev emulation handles pgprot_decrypted() internally via the
Prime helpers. Fbdev doesn't have to do anything in this case. In
cases where DRM uses deferred I/O, this patch updates fb_mmap correctly.

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: Fix incorrect page mapping clearance at fb_deferred_io_release()

The recent fix for the deferred I/O by the commit
3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O d

fbdev: Fix incorrect page mapping clearance at fb_deferred_io_release()

The recent fix for the deferred I/O by the commit
3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices")
caused a regression when the same fb device is opened/closed while
it's being used. It resulted in a frozen screen even if something
is redrawn there after the close. The breakage is because the patch
was made under a wrong assumption of a single open; in the current
code, fb_deferred_io_release() cleans up the page mapping of the
pageref list and it calls cancel_delayed_work_sync() unconditionally,
where both are no correct behavior for multiple opens.

This patch adds a refcount for the opens of the device, and applies
the cleanup only when all files get closed.

As both fb_deferred_io_open() and _close() are called always in the
fb_info lock (mutex), it's safe to use the normal int for the
refcounting.

Also, a useless BUG_ON() is dropped.

Fixes: 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices")
Cc: <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Reviewed-by: Patrik Jakobsson <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: Fix invalid page access after closing deferred I/O devices

When a fbdev with deferred I/O is once opened and closed, the dirty
pages still remain queued in the pageref list, and eventually la

fbdev: Fix invalid page access after closing deferred I/O devices

When a fbdev with deferred I/O is once opened and closed, the dirty
pages still remain queued in the pageref list, and eventually later
those may be processed in the delayed work. This may lead to a
corruption of pages, hitting an Oops.

This patch makes sure to cancel the delayed work and clean up the
pageref list at closing the device for addressing the bug. A part of
the cleanup code is factored out as a new helper function that is
called from the common fb_release().

Reviewed-by: Patrik Jakobsson <[email protected]>
Cc: <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Tested-by: Miko Larsson <[email protected]>
Fixes: 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct")
Reviewed-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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mm: replace vma->vm_flags direct modifications with modifier calls

Replace direct modifications to vma->vm_flags with calls to modifier
functions to be able to track flag changes and to keep vma loc

mm: replace vma->vm_flags direct modifications with modifier calls

Replace direct modifications to vma->vm_flags with calls to modifier
functions to be able to track flag changes and to keep vma locking
correctness.

[[email protected]: fix drivers/misc/open-dice.c, per Hyeonggon Yoo]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Acked-by: Mike Rapoport (IBM) <[email protected]>
Acked-by: Sebastian Reichel <[email protected]>
Reviewed-by: Liam R. Howlett <[email protected]>
Reviewed-by: Hyeonggon Yoo <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arjun Roy <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Howells <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Oskolkov <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Punit Agrawal <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Soheil Hassas Yeganeh <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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fbdev: Remove unused struct fb_deferred_io .first_io field

This optional callback was added in the commit 1f45f9dbb392 ("fb_defio:
add first_io callback") but it was never used by a driver. Let's re

fbdev: Remove unused struct fb_deferred_io .first_io field

This optional callback was added in the commit 1f45f9dbb392 ("fb_defio:
add first_io callback") but it was never used by a driver. Let's remove
it since it's unlikely that will be used after a decade that was added.

Signed-off-by: Javier Martinez Canillas <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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Revert "drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer"

This reverts commit 7f5cc4a3e5e4c5a38e5748defc952e45278f7a70.

Needed to restore the fbdev damage worker. There have

Revert "drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer"

This reverts commit 7f5cc4a3e5e4c5a38e5748defc952e45278f7a70.

Needed to restore the fbdev damage worker. There have been bug reports
about locking order [1] and incorrectly takens branches. [2] Restore
the damage worker until these problems have been resovled.

Signed-off-by: Thomas Zimmermann <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Link: https://intel-gfx-ci.01.org/tree/drm-tip/fi-kbl-8809g.html # 1
Link: https://lore.kernel.org/dri-devel/[email protected]/T/#m06eedc0a468940e4cbbd14ca026733b639bc445a # 2
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

show more ...

Revert "drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer"

This reverts commit 7f5cc4a3e5e4c5a38e5748defc952e45278f7a70.

Needed to restore the fbdev damage worker. There have

Revert "drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer"

This reverts commit 7f5cc4a3e5e4c5a38e5748defc952e45278f7a70.

Needed to restore the fbdev damage worker. There have been bug reports
about locking order [1] and incorrectly takens branches. [2] Restore
the damage worker until these problems have been resovled.

Signed-off-by: Thomas Zimmermann <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Link: https://intel-gfx-ci.01.org/tree/drm-tip/fi-kbl-8809g.html # 1
Link: https://lore.kernel.org/dri-devel/[email protected]/T/#m06eedc0a468940e4cbbd14ca026733b639bc445a # 2
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 8b83e1a455382dc667898a525a93f4eb6716cc41)

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drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer

Schedule the deferred-I/O worker instead of the damage worker after
writing to the fbdev framebuffer. The deferred-I/O worker

drm/fb-helper: Schedule deferred-I/O worker after writing to framebuffer

Schedule the deferred-I/O worker instead of the damage worker after
writing to the fbdev framebuffer. The deferred-I/O worker then performs
the dirty-fb update. The fbdev emulation will initialize deferred I/O
for all drivers that require damage updates. It is therefore a valid
assumption that the deferred-I/O worker is present.

It would be possible to perform the damage handling directly from within
the write operation. But doing this could increase the overhead of the
write or interfere with a concurrently scheduled deferred-I/O worker.
Instead, scheduling the deferred-I/O worker with its regular delay of
50 ms removes load off the write operation and allows the deferred-I/O
worker to handle multiple write operations that arrived during the delay
time window.

v3:
* remove unused variable (lkp)
v2:
* keep drm_fb_helper_damage() (Daniel)
* use fb_deferred_io_schedule_flush() (Daniel)
* clarify comments (Daniel)

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Daniel Vetter <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: Rename pagelist to pagereflist for deferred I/O

Rename various instances of pagelist to pagereflist. The list now
stores pageref structures, so the new name is more appropriate.

In their wri

fbdev: Rename pagelist to pagereflist for deferred I/O

Rename various instances of pagelist to pagereflist. The list now
stores pageref structures, so the new name is more appropriate.

In their write-back helpers, several fbdev drivers refer to the
pageref list in struct fb_deferred_io instead of using the one
supplied as argument to the function. Convert them over to the
supplied one. It's the same instance, so no change of behavior
occurs.

v4:
* fix commit message (Javier)

Suggested-by: Sam Ravnborg <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: Refactor implementation of page_mkwrite

Refactor the page-write handler for deferred I/O. Drivers use the
function to let fbdev track written pages of mmap'ed framebuffer
memory.

v3:
* keep

fbdev: Refactor implementation of page_mkwrite

Refactor the page-write handler for deferred I/O. Drivers use the
function to let fbdev track written pages of mmap'ed framebuffer
memory.

v3:
* keep locking within track-pages function for readability (Sam)
v2:
* don't export the helper until we have an external caller

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

show more ...

fbdev: Track deferred-I/O pages in pageref struct

Store the per-page state for fbdev's deferred I/O in struct
fb_deferred_io_pageref. Maintain a list of pagerefs for the pages
that have to be writte

fbdev: Track deferred-I/O pages in pageref struct

Store the per-page state for fbdev's deferred I/O in struct
fb_deferred_io_pageref. Maintain a list of pagerefs for the pages
that have to be written back to video memory. Update all affected
drivers.

As with pages before, fbdev acquires a pageref when an mmaped page
of the framebuffer is being written to. It holds the pageref in a
list of all currently written pagerefs until it flushes the written
pages to video memory. Writeback occurs periodically. After writeback
fbdev releases all pagerefs and builds up a new dirty list until the
next writeback occurs.

Using pagerefs has a number of benefits.

For pages of the framebuffer, the deferred I/O code used struct
page.lru as an entry into the list of dirty pages. The lru field is
owned by the page cache, which makes deferred I/O incompatible with
some memory pages (e.g., most notably DRM's GEM SHMEM allocator).
struct fb_deferred_io_pageref now provides an entry into a list of
dirty framebuffer pages, freeing lru for use with the page cache.

Drivers also assumed that struct page.index is the page offset into
the framebuffer. This is not true for DRM buffers, which are located
at various offset within a mapped area. struct fb_deferred_io_pageref
explicitly stores an offset into the framebuffer. struct page.index
is now only the page offset into the mapped area.

These changes will allow DRM to use fbdev deferred I/O without an
intermediate shadow buffer.

v3:
* use pageref->offset for sorting
* fix grammar in comment
v2:
* minor fixes in commit message

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: Put mmap for deferred I/O into drivers

The fbdev mmap function fb_mmap() unconditionally overrides the
driver's implementation if deferred I/O has been activated. This
makes it hard to implem

fbdev: Put mmap for deferred I/O into drivers

The fbdev mmap function fb_mmap() unconditionally overrides the
driver's implementation if deferred I/O has been activated. This
makes it hard to implement mmap with anything but a vmalloc()'ed
software buffer. That is specifically a problem for DRM, where
video memory is maintained by a memory manager.

Leave the mmap handling to drivers and expect them to call the
helper for deferred I/O by thmeselves.

v4:
* unlock mm_lock in fb_mmap() error path (Dan)
v3:
* fix warning if fb_mmap is missing (kernel test robot)
v2:
* print a helpful error message if the defio setup is
incorrect (Javier)

Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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fbdev: defio: fix the pagelist corruption

Easily hit the below list corruption:
==
list_add corruption. prev->next should be next (ffffffffc0ceb090), but
was ffffec604507edc8. (prev=ffffec604507edc8

fbdev: defio: fix the pagelist corruption

Easily hit the below list corruption:
==
list_add corruption. prev->next should be next (ffffffffc0ceb090), but
was ffffec604507edc8. (prev=ffffec604507edc8).
WARNING: CPU: 65 PID: 3959 at lib/list_debug.c:26
__list_add_valid+0x53/0x80
CPU: 65 PID: 3959 Comm: fbdev Tainted: G U
RIP: 0010:__list_add_valid+0x53/0x80
Call Trace:
<TASK>
fb_deferred_io_mkwrite+0xea/0x150
do_page_mkwrite+0x57/0xc0
do_wp_page+0x278/0x2f0
__handle_mm_fault+0xdc2/0x1590
handle_mm_fault+0xdd/0x2c0
do_user_addr_fault+0x1d3/0x650
exc_page_fault+0x77/0x180
? asm_exc_page_fault+0x8/0x30
asm_exc_page_fault+0x1e/0x30
RIP: 0033:0x7fd98fc8fad1
==

Figure out the race happens when one process is adding &page->lru into
the pagelist tail in fb_deferred_io_mkwrite(), another process is
re-initializing the same &page->lru in fb_deferred_io_fault(), which is
not protected by the lock.

This fix is to init all the page lists one time during initialization,
it not only fixes the list corruption, but also avoids INIT_LIST_HEAD()
redundantly.

V2: change "int i" to "unsigned int i" (Geert Uytterhoeven)

Signed-off-by: Chuansheng Liu <[email protected]>
Fixes: 105a940416fc ("fbdev/defio: Early-out if page is already enlisted")
Cc: Thomas Zimmermann <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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