Messages in this thread | | | Subject | Re: [PATCH 17/19] powerpc: book3s64: convert to pin_user_pages() and put_user_page() | From | John Hubbard <> | Date | Mon, 25 Nov 2019 12:46:56 -0800 |
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On 11/25/19 12:59 AM, Jan Kara wrote: > On Sun 24-11-19 20:20:09, John Hubbard wrote: >> 1. Convert from get_user_pages() to pin_user_pages(). >> >> 2. As required by pin_user_pages(), release these pages via >> put_user_page(). In this case, do so via put_user_pages_dirty_lock(). >> >> That has the side effect of calling set_page_dirty_lock(), instead >> of set_page_dirty(). This is probably more accurate. >> >> As Christoph Hellwig put it, "set_page_dirty() is only safe if we are >> dealing with a file backed page where we have reference on the inode it >> hangs off." [1] >> >> 3. Release each page in mem->hpages[] (instead of mem->hpas[]), because >> that is the array that pin_longterm_pages() filled in. This is more >> accurate and should be a little safer from a maintenance point of >> view. > > Except that this breaks the code. hpages is unioned with hpas... >
OK.
>> @@ -212,10 +211,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem) >> if (!page) >> continue; >> >> - if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY) >> - SetPageDirty(page); >> + put_user_pages_dirty_lock(&mem->hpages[i], 1, >> + MM_IOMMU_TABLE_GROUP_PAGE_DIRTY); > > And the dirtying condition is wrong here as well. Currently it is always > true. > > Honza >
Yes. Fixed up locally. The function now looks like this (for this patch, not for the entire series, which renames "put" to "unpin"):
static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem) { long i; struct page *page = NULL;
if (!mem->hpas) return;
for (i = 0; i < mem->entries; ++i) { if (!mem->hpas[i]) continue;
page = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT); if (!page) continue;
put_user_pages_dirty_lock(&page, 1, mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY);
mem->hpas[i] = 0; } }
thanks, -- John Hubbard NVIDIA
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