mm: xip fix fault vs sparse page invalidate race (538f8ea6) · Commits · 戴 / test

mm/filemap_xip.c

+46 −14

Original line number	Diff line number	Diff line
		@@ -15,6 +15,8 @@
		#include <linux/rmap.h>
		#include <linux/mmu_notifier.h>
		#include <linux/sched.h>
		#include <linux/seqlock.h>
		#include <linux/mutex.h>
		#include <asm/tlbflush.h>
		#include <asm/io.h>

		@@ -22,22 +24,18 @@
		* We do use our own empty page to avoid interference with other users
		* of ZERO_PAGE(), such as /dev/zero
		*/
		static DEFINE_MUTEX(xip_sparse_mutex);
		static seqcount_t xip_sparse_seq = SEQCNT_ZERO;
		static struct page *__xip_sparse_page;

		/* called under xip_sparse_mutex */
		static struct page *xip_sparse_page(void)
		{
		if (!__xip_sparse_page) {
		struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_ZERO);

		if (page) {
		static DEFINE_SPINLOCK(xip_alloc_lock);
		spin_lock(&xip_alloc_lock);
		if (!__xip_sparse_page)
		if (page)
		__xip_sparse_page = page;
		else
		__free_page(page);
		spin_unlock(&xip_alloc_lock);
		}
		}
		return __xip_sparse_page;
		}
		@@ -174,11 +172,16 @@ __xip_unmap (struct address_space * mapping,
		pte_t pteval;
		spinlock_t *ptl;
		struct page *page;
		unsigned count;
		int locked = 0;

		count = read_seqcount_begin(&xip_sparse_seq);

		page = __xip_sparse_page;
		if (!page)
		return;

		retry:
		spin_lock(&mapping->i_mmap_lock);
		vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
		mm = vma->vm_mm;
		@@ -198,6 +201,14 @@ __xip_unmap (struct address_space * mapping,
		}
		}
		spin_unlock(&mapping->i_mmap_lock);

		if (locked) {
		mutex_unlock(&xip_sparse_mutex);
		} else if (read_seqcount_retry(&xip_sparse_seq, count)) {
		mutex_lock(&xip_sparse_mutex);
		locked = 1;
		goto retry;
		}
		}

		/*
		@@ -218,7 +229,7 @@ static int xip_file_fault(struct vm_area_struct vma, struct vm_fault vmf)
		int error;

		/* XXX: are VM_FAULT_ codes OK? */

		again:
		size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
		if (vmf->pgoff >= size)
		return VM_FAULT_SIGBUS;
		@@ -245,6 +256,7 @@ static int xip_file_fault(struct vm_area_struct vma, struct vm_fault vmf)
		__xip_unmap(mapping, vmf->pgoff);

		found:
		printk("%s insert %lx@%lx\n", current->comm, (unsigned long)vmf->virtual_address, xip_pfn);
		err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
		xip_pfn);
		if (err == -ENOMEM)
		@@ -252,14 +264,34 @@ found:
		BUG_ON(err);
		return VM_FAULT_NOPAGE;
		} else {
		int err, ret = VM_FAULT_OOM;

		mutex_lock(&xip_sparse_mutex);
		write_seqcount_begin(&xip_sparse_seq);
		error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
		&xip_mem, &xip_pfn);
		if (unlikely(!error)) {
		write_seqcount_end(&xip_sparse_seq);
		mutex_unlock(&xip_sparse_mutex);
		goto again;
		}
		if (error != -ENODATA)
		goto out;
		/* not shared and writable, use xip_sparse_page() */
		page = xip_sparse_page();
		if (!page)
		return VM_FAULT_OOM;
		goto out;
		err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
		page);
		if (err == -ENOMEM)
		goto out;

		page_cache_get(page);
		vmf->page = page;
		return 0;
		ret = VM_FAULT_NOPAGE;
		out:
		write_seqcount_end(&xip_sparse_seq);
		mutex_unlock(&xip_sparse_mutex);

		return ret;
		}
		}

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