forked from luck/tmp_suning_uos_patched
dax: provide diagnostics for pmd mapping failures
There is a wide gamut of conditions that can trigger the dax pmd path to fallback to pte mappings. Ideally we'd have a syscall interface to determine mapping characteristics after the fact. In the meantime provide debug messages. Signed-off-by: Dan Williams <dan.j.williams@intel.com> Suggested-by: Matthew Wilcox <willy@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
3565fce3a6
commit
cbb38e41a9
65
fs/dax.c
65
fs/dax.c
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@ -558,6 +558,24 @@ EXPORT_SYMBOL_GPL(dax_fault);
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*/
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#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
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static void __dax_dbg(struct buffer_head *bh, unsigned long address,
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const char *reason, const char *fn)
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{
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if (bh) {
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char bname[BDEVNAME_SIZE];
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bdevname(bh->b_bdev, bname);
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pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
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"length %zd fallback: %s\n", fn, current->comm,
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address, bname, bh->b_state, (u64)bh->b_blocknr,
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bh->b_size, reason);
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} else {
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pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
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current->comm, address, reason);
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}
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}
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#define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd")
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int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmd, unsigned int flags, get_block_t get_block,
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dax_iodone_t complete_unwritten)
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@ -581,21 +599,29 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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/* Fall back to PTEs if we're going to COW */
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if (write && !(vma->vm_flags & VM_SHARED)) {
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split_huge_pmd(vma, pmd, address);
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dax_pmd_dbg(NULL, address, "cow write");
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return VM_FAULT_FALLBACK;
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}
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/* If the PMD would extend outside the VMA */
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if (pmd_addr < vma->vm_start)
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if (pmd_addr < vma->vm_start) {
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dax_pmd_dbg(NULL, address, "vma start unaligned");
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return VM_FAULT_FALLBACK;
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if ((pmd_addr + PMD_SIZE) > vma->vm_end)
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}
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if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
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dax_pmd_dbg(NULL, address, "vma end unaligned");
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return VM_FAULT_FALLBACK;
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}
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pgoff = linear_page_index(vma, pmd_addr);
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size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
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if (pgoff >= size)
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return VM_FAULT_SIGBUS;
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/* If the PMD would cover blocks out of the file */
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if ((pgoff | PG_PMD_COLOUR) >= size)
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if ((pgoff | PG_PMD_COLOUR) >= size) {
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dax_pmd_dbg(NULL, address,
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"offset + huge page size > file size");
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return VM_FAULT_FALLBACK;
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}
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memset(&bh, 0, sizeof(bh));
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block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
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@ -611,8 +637,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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* just fall back to PTEs. Calling get_block 512 times in a loop
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* would be silly.
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*/
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if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
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if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
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dax_pmd_dbg(&bh, address, "allocated block too small");
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goto fallback;
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}
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/*
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* If we allocated new storage, make sure no process has any
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@ -635,23 +663,33 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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result = VM_FAULT_SIGBUS;
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goto out;
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}
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if ((pgoff | PG_PMD_COLOUR) >= size)
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if ((pgoff | PG_PMD_COLOUR) >= size) {
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dax_pmd_dbg(&bh, address, "pgoff unaligned");
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goto fallback;
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}
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if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
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spinlock_t *ptl;
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pmd_t entry;
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struct page *zero_page = get_huge_zero_page();
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if (unlikely(!zero_page))
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if (unlikely(!zero_page)) {
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dax_pmd_dbg(&bh, address, "no zero page");
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goto fallback;
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}
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ptl = pmd_lock(vma->vm_mm, pmd);
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if (!pmd_none(*pmd)) {
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spin_unlock(ptl);
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dax_pmd_dbg(&bh, address, "pmd already present");
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goto fallback;
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}
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dev_dbg(part_to_dev(bdev->bd_part),
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"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
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__func__, current->comm, address,
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(unsigned long long) to_sector(&bh, inode));
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entry = mk_pmd(zero_page, vma->vm_page_prot);
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entry = pmd_mkhuge(entry);
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set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
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@ -668,8 +706,13 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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result = VM_FAULT_SIGBUS;
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goto out;
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}
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if (length < PMD_SIZE
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|| (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)) {
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if (length < PMD_SIZE) {
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dax_pmd_dbg(&bh, address, "dax-length too small");
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dax_unmap_atomic(bdev, &dax);
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goto fallback;
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}
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if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
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dax_pmd_dbg(&bh, address, "pfn unaligned");
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dax_unmap_atomic(bdev, &dax);
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goto fallback;
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}
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@ -680,6 +723,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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*/
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if (pfn_t_has_page(dax.pfn)) {
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dax_unmap_atomic(bdev, &dax);
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dax_pmd_dbg(&bh, address, "pfn not in memmap");
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goto fallback;
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}
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@ -692,6 +736,11 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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}
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dax_unmap_atomic(bdev, &dax);
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dev_dbg(part_to_dev(bdev->bd_part),
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"%s: %s addr: %lx pfn: %lx sect: %llx\n",
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__func__, current->comm, address,
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pfn_t_to_pfn(dax.pfn),
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(unsigned long long) dax.sector);
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result |= vmf_insert_pfn_pmd(vma, address, pmd,
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dax.pfn, write);
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}
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