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sg_miter_start() is currently unaware of the direction of the copy
process (to or from the scatter list). It is important to know the
direction because the page has to be flushed in case the data written
is seen on a different mapping in user land on cache incoherent
architectures.
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Acked-by: FUJITA Tomonori <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Pierre Ossman <[email protected]>
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Impact: fix not-so-critical but annoying bug
sg_miter_next() returns 0 sized mapping if there is an zero sized sg
entry in the list or at the end of each iteration. As the users
always check the ->length field, this bug shouldn't be critical other
than causing unnecessary iteration.
Fix it.
Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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kunmap() takes as argument the struct page that orginally got kmap()'d,
however the sg_miter_stop() function passed it the kernel virtual address
instead, resulting in weird stuff.
Somehow I ended up fixing this bug by accident while looking for a bug in
the same area.
Reported-by: kerneloops.org
Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Arjan van de Ven <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: <[email protected]> [2.6.27.x]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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The callers of sg_copy_buffer must disable interrupts before calling
it (since it uses kmap_atomic). Some callers use it on
interrupt-disabled code but some need to take the trouble to disable
interrupts just for this. No wonder they forget about it and we hit a
bug like:
http://bugzilla.kernel.org/show_bug.cgi?id=11529
James said that it might be better to disable interrupts inside the
function rather than risk the callers getting it wrong.
Signed-off-by: FUJITA Tomonori <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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This is alternative implementation of sg content iterator introduced
by commit 83e7d317... from Pierre Ossman in next-20080716. As there's
already an sg iterator which iterates over sg entries themselves, name
this sg_mapping_iterator.
Slightly edited description from the original implementation follows.
Iteration over a sg list is not that trivial when you take into
account that memory pages might have to be mapped before being used.
Unfortunately, that means that some parts of the kernel restrict
themselves to directly accesible memory just to not have to deal with
the mess.
This patch adds a simple iterator system that allows any code to
easily traverse an sg list and not have to deal with all the details.
The user can decide to consume part of the iteration. Also, iteration
can be stopped and resumed later if releasing the kmap between
iteration steps is necessary. These features are useful to implement
piecemeal sg copying for interrupt drive PIO for example.
Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: Pierre Ossman <[email protected]>
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This patch adds new three helper functions to copy data between an SG
list and a linear buffer.
- sg_copy_from_buffer copies data from linear buffer to an SG list
- sg_copy_to_buffer copies data from an SG list to a linear buffer
When the APIs copy data from a linear buffer to an SG list,
flush_kernel_dcache_page is called. It's not necessary for everyone
but it's a no-op on most architectures and in general the API is not
used in performance critical path.
Signed-off-by: FUJITA Tomonori <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
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SCSI sg table allocation has a maximum size (of SCSI_MAX_SG_SEGMENTS,
currently 128) and this will cause a BUG_ON() in SCSI if something
tries an allocation over it. This patch adds a size limit to the
chaining allocator to allow the specification of the maximum
allocation size for chaining, so we always chain in units of the
maximum SCSI allocation size.
Signed-off-by: James Bottomley <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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Manually doing chained sg lists is not trivial, so add some helpers
to make sure that drivers get it right.
Signed-off-by: Jens Axboe <[email protected]>
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