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    Subject[PATCH v5 10/17] dax: remove dax_pmd_fault()
    Date
    dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
    fault handler. This fault handler has been disabled for several kernel
    releases, and support for PMDs will be reintroduced using the struct iomap
    interface instead.

    Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Jan Kara <jack@suse.cz>
    ---
    fs/dax.c | 213 ----------------------------------------------------
    include/linux/dax.h | 6 +-
    2 files changed, 1 insertion(+), 218 deletions(-)

    diff --git a/fs/dax.c b/fs/dax.c
    index 608cee9..1b9154a 100644
    --- a/fs/dax.c
    +++ b/fs/dax.c
    @@ -908,219 +908,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
    }
    EXPORT_SYMBOL_GPL(dax_fault);

    -#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
    -/*
    - * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
    - * more often than one might expect in the below function.
    - */
    -#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
    -
    -static void __dax_dbg(struct buffer_head *bh, unsigned long address,
    - const char *reason, const char *fn)
    -{
    - if (bh) {
    - char bname[BDEVNAME_SIZE];
    - bdevname(bh->b_bdev, bname);
    - pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
    - "length %zd fallback: %s\n", fn, current->comm,
    - address, bname, bh->b_state, (u64)bh->b_blocknr,
    - bh->b_size, reason);
    - } else {
    - pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
    - current->comm, address, reason);
    - }
    -}
    -
    -#define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd")
    -
    -/**
    - * dax_pmd_fault - handle a PMD fault on a DAX file
    - * @vma: The virtual memory area where the fault occurred
    - * @vmf: The description of the fault
    - * @get_block: The filesystem method used to translate file offsets to blocks
    - *
    - * When a page fault occurs, filesystems may call this helper in their
    - * pmd_fault handler for DAX files.
    - */
    -int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
    - pmd_t *pmd, unsigned int flags, get_block_t get_block)
    -{
    - 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 pmd_addr = address & PMD_MASK;
    - bool write = flags & FAULT_FLAG_WRITE;
    - struct block_device *bdev;
    - pgoff_t size, pgoff;
    - sector_t block;
    - int result = 0;
    - bool alloc = false;
    -
    - /* dax pmd 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_pmd(vma, pmd, address);
    - dax_pmd_dbg(NULL, address, "cow write");
    - return VM_FAULT_FALLBACK;
    - }
    - /* If the PMD would extend outside the VMA */
    - if (pmd_addr < vma->vm_start) {
    - dax_pmd_dbg(NULL, address, "vma start unaligned");
    - return VM_FAULT_FALLBACK;
    - }
    - if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
    - dax_pmd_dbg(NULL, address, "vma end unaligned");
    - return VM_FAULT_FALLBACK;
    - }
    -
    - pgoff = linear_page_index(vma, pmd_addr);
    - size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
    - if (pgoff >= size)
    - return VM_FAULT_SIGBUS;
    - /* If the PMD would cover blocks out of the file */
    - if ((pgoff | PG_PMD_COLOUR) >= size) {
    - dax_pmd_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 = PMD_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;
    - WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
    - }
    -
    - bdev = bh.b_bdev;
    -
    - if (bh.b_size < PMD_SIZE) {
    - dax_pmd_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 + PMD_SIZE - 1; /* inclusive */
    -
    - truncate_pagecache_range(inode, lstart, lend);
    - }
    -
    - if (!write && !buffer_mapped(&bh)) {
    - spinlock_t *ptl;
    - pmd_t entry;
    - struct page *zero_page = get_huge_zero_page();
    -
    - if (unlikely(!zero_page)) {
    - dax_pmd_dbg(&bh, address, "no zero page");
    - goto fallback;
    - }
    -
    - ptl = pmd_lock(vma->vm_mm, pmd);
    - if (!pmd_none(*pmd)) {
    - spin_unlock(ptl);
    - dax_pmd_dbg(&bh, address, "pmd already present");
    - goto fallback;
    - }
    -
    - dev_dbg(part_to_dev(bdev->bd_part),
    - "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
    - __func__, current->comm, address,
    - (unsigned long long) to_sector(&bh, inode));
    -
    - entry = mk_pmd(zero_page, vma->vm_page_prot);
    - entry = pmd_mkhuge(entry);
    - set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
    - result = VM_FAULT_NOPAGE;
    - spin_unlock(ptl);
    - } else {
    - struct blk_dax_ctl dax = {
    - .sector = to_sector(&bh, inode),
    - .size = PMD_SIZE,
    - };
    - long length = dax_map_atomic(bdev, &dax);
    -
    - if (length < 0) {
    - dax_pmd_dbg(&bh, address, "dax-error fallback");
    - goto fallback;
    - }
    - if (length < PMD_SIZE) {
    - dax_pmd_dbg(&bh, address, "dax-length too small");
    - dax_unmap_atomic(bdev, &dax);
    - goto fallback;
    - }
    - if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
    - dax_pmd_dbg(&bh, address, "pfn unaligned");
    - dax_unmap_atomic(bdev, &dax);
    - goto fallback;
    - }
    -
    - if (!pfn_t_devmap(dax.pfn)) {
    - dax_unmap_atomic(bdev, &dax);
    - dax_pmd_dbg(&bh, address, "pfn not in memmap");
    - goto fallback;
    - }
    - dax_unmap_atomic(bdev, &dax);
    -
    - /*
    - * For PTE faults we insert a radix tree entry for reads, and
    - * leave it clean. Then on the first write we dirty the radix
    - * tree entry via the dax_pfn_mkwrite() path. This sequence
    - * allows the dax_pfn_mkwrite() call to be simpler and avoid a
    - * call into get_block() to translate the pgoff to a sector in
    - * order to be able to create a new radix tree entry.
    - *
    - * The PMD path doesn't have an equivalent to
    - * dax_pfn_mkwrite(), though, so for a read followed by a
    - * write we traverse all the way through dax_pmd_fault()
    - * twice. This means we can just skip inserting a radix tree
    - * entry completely on the initial read and just wait until
    - * the write to insert a dirty entry.
    - */
    - if (write) {
    - /*
    - * We should insert radix-tree entry and dirty it here.
    - * For now this is broken...
    - */
    - }
    -
    - 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_pmd(vma, address, pmd,
    - dax.pfn, write);
    - }
    -
    - out:
    - return result;
    -
    - fallback:
    - count_vm_event(THP_FAULT_FALLBACK);
    - result = VM_FAULT_FALLBACK;
    - goto out;
    -}
    -EXPORT_SYMBOL_GPL(dax_pmd_fault);
    -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
    -
    /**
    * dax_pfn_mkwrite - handle first write to DAX page
    * @vma: The virtual memory area where the fault occurred
    diff --git a/include/linux/dax.h b/include/linux/dax.h
    index a41a747..0f74866 100644
    --- a/include/linux/dax.h
    +++ b/include/linux/dax.h
    @@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
    }
    #endif

    -#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
    -int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
    - unsigned int flags, get_block_t);
    -#else
    static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
    pmd_t *pmd, unsigned int flags, get_block_t gb)
    {
    return VM_FAULT_FALLBACK;
    }
    -#endif
    +
    int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
    #define dax_mkwrite(vma, vmf, gb) dax_fault(vma, vmf, gb)

    --
    2.7.4
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      Last update: 2016-10-07 23:13    [W:4.120 / U:0.716 seconds]
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