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Date: Sun, 31 Jan 2016 23:09:34 +1100
From: Matthew Wilcox <matthew.r.wilcox@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <willy@...ux.intel.com>, linux-mm@...ck.org,
linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH v4 7/8] dax: Support for transparent PUD pages
From: Matthew Wilcox <willy@...ux.intel.com>
The DAX support for transparent huge PUD pages
Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
---
fs/dax.c | 185 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 185 insertions(+)
diff --git a/fs/dax.c b/fs/dax.c
index b2ad0ce..2f9bb89 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -958,6 +958,189 @@ static int dax_pmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
}
#endif /* !CONFIG_TRANSPARENT_HUGEPAGE */
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+/*
+ * The 'colour' (ie low bits) within a PUD of a page offset. This comes up
+ * more often than one might expect in the below function.
+ */
+#define PG_PUD_COLOUR ((PUD_SIZE >> PAGE_SHIFT) - 1)
+
+#define dax_pud_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pud")
+
+static int dax_pud_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+ get_block_t get_block, dax_iodone_t complete_unwritten)
+{
+ struct file *file = vma->vm_file;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ struct buffer_head bh;
+ unsigned blkbits = inode->i_blkbits;
+ unsigned long address = (unsigned long)vmf->virtual_address;
+ unsigned long pud_addr = address & PUD_MASK;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+ struct block_device *bdev;
+ pgoff_t size, pgoff;
+ sector_t block;
+ int result = 0;
+ bool alloc = false;
+
+ /* dax pud mappings require pfn_t_devmap() */
+ if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
+ return VM_FAULT_FALLBACK;
+
+ /* Fall back to PTEs if we're going to COW */
+ if (write && !(vma->vm_flags & VM_SHARED)) {
+ split_huge_pud(vma, vmf->pud, address);
+ dax_pud_dbg(NULL, address, "cow write");
+ return VM_FAULT_FALLBACK;
+ }
+ /* If the PUD would extend outside the VMA */
+ if (pud_addr < vma->vm_start) {
+ dax_pud_dbg(NULL, address, "vma start unaligned");
+ return VM_FAULT_FALLBACK;
+ }
+ if ((pud_addr + PUD_SIZE) > vma->vm_end) {
+ dax_pud_dbg(NULL, address, "vma end unaligned");
+ return VM_FAULT_FALLBACK;
+ }
+
+ pgoff = linear_page_index(vma, pud_addr);
+ size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ if (pgoff >= size)
+ return VM_FAULT_SIGBUS;
+ /* If the PUD would cover blocks out of the file */
+ if ((pgoff | PG_PUD_COLOUR) >= size) {
+ dax_pud_dbg(NULL, address,
+ "offset + huge page size > file size");
+ return VM_FAULT_FALLBACK;
+ }
+
+ memset(&bh, 0, sizeof(bh));
+ bh.b_bdev = inode->i_sb->s_bdev;
+ block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
+
+ bh.b_size = PUD_SIZE;
+
+ if (get_block(inode, block, &bh, 0) != 0)
+ return VM_FAULT_SIGBUS;
+
+ if (!buffer_mapped(&bh) && write) {
+ if (get_block(inode, block, &bh, 1) != 0)
+ return VM_FAULT_SIGBUS;
+ alloc = true;
+ }
+
+ bdev = bh.b_bdev;
+
+ /*
+ * If the filesystem isn't willing to tell us the length of a hole,
+ * just fall back to PMDs. Calling get_block 512 times in a loop
+ * would be silly.
+ */
+ if (!buffer_size_valid(&bh) || bh.b_size < PUD_SIZE) {
+ dax_pud_dbg(&bh, address, "allocated block too small");
+ return VM_FAULT_FALLBACK;
+ }
+
+ /*
+ * If we allocated new storage, make sure no process has any
+ * zero pages covering this hole
+ */
+ if (alloc) {
+ loff_t lstart = pgoff << PAGE_SHIFT;
+ loff_t lend = lstart + PUD_SIZE - 1; /* inclusive */
+
+ truncate_pagecache_range(inode, lstart, lend);
+ }
+
+ i_mmap_lock_read(mapping);
+
+ /*
+ * If a truncate happened while we were allocating blocks, we may
+ * leave blocks allocated to the file that are beyond EOF. We can't
+ * take i_mutex here, so just leave them hanging; they'll be freed
+ * when the file is deleted.
+ */
+ size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ if (pgoff >= size) {
+ result = VM_FAULT_SIGBUS;
+ goto out;
+ }
+ if ((pgoff | PG_PUD_COLOUR) >= size) {
+ dax_pud_dbg(&bh, address, "page extends outside VMA");
+ goto fallback;
+ }
+
+ if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
+ dax_pud_dbg(&bh, address, "no zero page");
+ goto fallback;
+ } else {
+ struct blk_dax_ctl dax = {
+ .sector = to_sector(&bh, inode),
+ .size = PUD_SIZE,
+ };
+ long length = dax_map_atomic(bdev, &dax);
+
+ if (length < 0) {
+ result = VM_FAULT_SIGBUS;
+ goto out;
+ }
+ if (length < PUD_SIZE) {
+ dax_pud_dbg(&bh, address, "dax-length too small");
+ dax_unmap_atomic(bdev, &dax);
+ goto fallback;
+ }
+ if (pfn_t_to_pfn(dax.pfn) & PG_PUD_COLOUR) {
+ dax_pud_dbg(&bh, address, "pfn unaligned");
+ dax_unmap_atomic(bdev, &dax);
+ goto fallback;
+ }
+
+ if (!pfn_t_devmap(dax.pfn)) {
+ dax_unmap_atomic(bdev, &dax);
+ dax_pud_dbg(&bh, address, "pfn not in memmap");
+ goto fallback;
+ }
+
+ if (buffer_unwritten(&bh) || buffer_new(&bh)) {
+ clear_pmem(dax.addr, PUD_SIZE);
+ wmb_pmem();
+ count_vm_event(PGMAJFAULT);
+ mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+ result |= VM_FAULT_MAJOR;
+ }
+ dax_unmap_atomic(bdev, &dax);
+
+ dev_dbg(part_to_dev(bdev->bd_part),
+ "%s: %s addr: %lx pfn: %lx sect: %llx\n",
+ __func__, current->comm, address,
+ pfn_t_to_pfn(dax.pfn),
+ (unsigned long long) dax.sector);
+ result |= vmf_insert_pfn_pud(vma, address, vmf->pud,
+ dax.pfn, write);
+ }
+
+ out:
+ i_mmap_unlock_read(mapping);
+
+ if (buffer_unwritten(&bh))
+ complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
+
+ return result;
+
+ fallback:
+ count_vm_event(THP_FAULT_FALLBACK);
+ result = VM_FAULT_FALLBACK;
+ goto out;
+}
+#else /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+static int dax_pud_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+ get_block_t get_block, dax_iodone_t complete_unwritten)
+{
+ return VM_FAULT_FALLBACK;
+}
+#endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
/**
* dax_fault - handle a page fault on a DAX file
* @vma: The virtual memory area where the fault occurred
@@ -982,6 +1165,8 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
return dax_pte_fault(vma, vmf, get_block, iodone);
case FAULT_FLAG_SIZE_PMD:
return dax_pmd_fault(vma, vmf, get_block, iodone);
+ case FAULT_FLAG_SIZE_PUD:
+ return dax_pud_fault(vma, vmf, get_block, iodone);
default:
return VM_FAULT_FALLBACK;
}
--
2.7.0.rc3
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