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| author |   Nicolin Chen <nicoleotsuka@gmail.com> | 2020-09-01 15:16:45 -0700 |
|---|---|---|
| committer |   Christoph Hellwig <hch@lst.de> | 2020-09-03 18:12:15 +0200 |
| commit | 1e9d90dbed120ec98517428ffff4dacd9797e39d (patch) | |
| tree | d743be6b54427bb62e36e6d1ae2f6fc243cd70b7 /drivers/parisc | |
| parent | mm: cma: use CMA_MAX_NAME to define the length of cma name array (diff) | |
| download | linux-dev-1e9d90dbed120ec98517428ffff4dacd9797e39d.tar.xz linux-dev-1e9d90dbed120ec98517428ffff4dacd9797e39d.zip | |
dma-mapping: introduce dma_get_seg_boundary_nr_pages()
We found that callers of dma_get_seg_boundary mostly do an ALIGN
with page mask and then do a page shift to get number of pages:
ALIGN(boundary + 1, 1 << shift) >> shift
However, the boundary might be as large as ULONG_MAX, which means
that a device has no specific boundary limit. So either "+ 1" or
passing it to ALIGN() would potentially overflow.
According to kernel defines:
#define ALIGN_MASK(x, mask) (((x) + (mask)) & ~(mask))
#define ALIGN(x, a) ALIGN_MASK(x, (typeof(x))(a) - 1)
We can simplify the logic here into a helper function doing:
ALIGN(boundary + 1, 1 << shift) >> shift
= ALIGN_MASK(b + 1, (1 << s) - 1) >> s
= {[b + 1 + (1 << s) - 1] & ~[(1 << s) - 1]} >> s
= [b + 1 + (1 << s) - 1] >> s
= [b + (1 << s)] >> s
= (b >> s) + 1
This patch introduces and applies dma_get_seg_boundary_nr_pages()
as an overflow-free helper for the dma_get_seg_boundary() callers
to get numbers of pages. It also takes care of the NULL dev case
for non-DMA API callers.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Acked-by: Niklas Schnelle <schnelle@linux.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'drivers/parisc')
| -rw-r--r-- | drivers/parisc/ccio-dma.c | 3 | ||||
| -rw-r--r-- | drivers/parisc/sba_iommu.c | 3 |
2 files changed, 2 insertions, 4 deletions
diff --git a/drivers/parisc/ccio-dma.c b/drivers/parisc/ccio-dma.c index a5507f75b524..ba16b7f8f806 100644 --- a/drivers/parisc/ccio-dma.c +++ b/drivers/parisc/ccio-dma.c @@ -356,8 +356,7 @@ ccio_alloc_range(struct ioc *ioc, struct device *dev, size_t size) ** ggg sacrifices another 710 to the computer gods. */ - boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1, - 1ULL << IOVP_SHIFT) >> IOVP_SHIFT; + boundary_size = dma_get_seg_boundary_nr_pages(dev, IOVP_SHIFT); if (pages_needed <= 8) { /* diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c index d4314fba0269..959bda193b96 100644 --- a/drivers/parisc/sba_iommu.c +++ b/drivers/parisc/sba_iommu.c @@ -342,8 +342,7 @@ sba_search_bitmap(struct ioc *ioc, struct device *dev, unsigned long shift; int ret; - boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1, - 1ULL << IOVP_SHIFT) >> IOVP_SHIFT; + boundary_size = dma_get_seg_boundary_nr_pages(dev, IOVP_SHIFT); #if defined(ZX1_SUPPORT) BUG_ON(ioc->ibase & ~IOVP_MASK); |