diff options
Diffstat (limited to 'fs/dax.c')
| -rw-r--r-- | fs/dax.c | 241 |
1 files changed, 241 insertions, 0 deletions
@@ -19,9 +19,13 @@ #include <linux/buffer_head.h> #include <linux/fs.h> #include <linux/genhd.h> +#include <linux/highmem.h> +#include <linux/memcontrol.h> +#include <linux/mm.h> #include <linux/mutex.h> #include <linux/sched.h> #include <linux/uio.h> +#include <linux/vmstat.h> int dax_clear_blocks(struct inode *inode, sector_t block, long size) { @@ -221,3 +225,240 @@ ssize_t dax_do_io(int rw, struct kiocb *iocb, struct inode *inode, return retval; } EXPORT_SYMBOL_GPL(dax_do_io); + +/* + * The user has performed a load from a hole in the file. Allocating + * a new page in the file would cause excessive storage usage for + * workloads with sparse files. We allocate a page cache page instead. + * We'll kick it out of the page cache if it's ever written to, + * otherwise it will simply fall out of the page cache under memory + * pressure without ever having been dirtied. + */ +static int dax_load_hole(struct address_space *mapping, struct page *page, + struct vm_fault *vmf) +{ + unsigned long size; + struct inode *inode = mapping->host; + if (!page) + page = find_or_create_page(mapping, vmf->pgoff, + GFP_KERNEL | __GFP_ZERO); + if (!page) + return VM_FAULT_OOM; + /* Recheck i_size under page lock to avoid truncate race */ + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (vmf->pgoff >= size) { + unlock_page(page); + page_cache_release(page); + return VM_FAULT_SIGBUS; + } + + vmf->page = page; + return VM_FAULT_LOCKED; +} + +static int copy_user_bh(struct page *to, struct buffer_head *bh, + unsigned blkbits, unsigned long vaddr) +{ + void *vfrom, *vto; + if (dax_get_addr(bh, &vfrom, blkbits) < 0) + return -EIO; + vto = kmap_atomic(to); + copy_user_page(vto, vfrom, vaddr, to); + kunmap_atomic(vto); + return 0; +} + +static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, + struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct address_space *mapping = inode->i_mapping; + sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); + unsigned long vaddr = (unsigned long)vmf->virtual_address; + void *addr; + unsigned long pfn; + pgoff_t size; + int error; + + i_mmap_lock_read(mapping); + + /* + * Check truncate didn't happen while we were allocating a block. + * If it did, this block may or may not be still allocated to the + * file. We can't tell the filesystem to free it because we can't + * take i_mutex here. In the worst case, the file still has blocks + * allocated past the end of the file. + */ + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (unlikely(vmf->pgoff >= size)) { + error = -EIO; + goto out; + } + + error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size); + if (error < 0) + goto out; + if (error < PAGE_SIZE) { + error = -EIO; + goto out; + } + + if (buffer_unwritten(bh) || buffer_new(bh)) + clear_page(addr); + + error = vm_insert_mixed(vma, vaddr, pfn); + + out: + i_mmap_unlock_read(mapping); + + if (bh->b_end_io) + bh->b_end_io(bh, 1); + + return error; +} + +static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, + get_block_t get_block) +{ + struct file *file = vma->vm_file; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + struct page *page; + struct buffer_head bh; + unsigned long vaddr = (unsigned long)vmf->virtual_address; + unsigned blkbits = inode->i_blkbits; + sector_t block; + pgoff_t size; + int error; + int major = 0; + + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (vmf->pgoff >= size) + return VM_FAULT_SIGBUS; + + memset(&bh, 0, sizeof(bh)); + block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits); + bh.b_size = PAGE_SIZE; + + repeat: + page = find_get_page(mapping, vmf->pgoff); + if (page) { + if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { + page_cache_release(page); + return VM_FAULT_RETRY; + } + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + page_cache_release(page); + goto repeat; + } + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (unlikely(vmf->pgoff >= size)) { + /* + * We have a struct page covering a hole in the file + * from a read fault and we've raced with a truncate + */ + error = -EIO; + goto unlock_page; + } + } + + error = get_block(inode, block, &bh, 0); + if (!error && (bh.b_size < PAGE_SIZE)) + error = -EIO; /* fs corruption? */ + if (error) + goto unlock_page; + + if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) { + if (vmf->flags & FAULT_FLAG_WRITE) { + error = get_block(inode, block, &bh, 1); + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + major = VM_FAULT_MAJOR; + if (!error && (bh.b_size < PAGE_SIZE)) + error = -EIO; + if (error) + goto unlock_page; + } else { + return dax_load_hole(mapping, page, vmf); + } + } + + if (vmf->cow_page) { + struct page *new_page = vmf->cow_page; + if (buffer_written(&bh)) + error = copy_user_bh(new_page, &bh, blkbits, vaddr); + else + clear_user_highpage(new_page, vaddr); + if (error) + goto unlock_page; + vmf->page = page; + if (!page) { + i_mmap_lock_read(mapping); + /* Check we didn't race with truncate */ + size = (i_size_read(inode) + PAGE_SIZE - 1) >> + PAGE_SHIFT; + if (vmf->pgoff >= size) { + i_mmap_unlock_read(mapping); + error = -EIO; + goto out; + } + } + return VM_FAULT_LOCKED; + } + + /* Check we didn't race with a read fault installing a new page */ + if (!page && major) + page = find_lock_page(mapping, vmf->pgoff); + + if (page) { + unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, + PAGE_CACHE_SIZE, 0); + delete_from_page_cache(page); + unlock_page(page); + page_cache_release(page); + } + + error = dax_insert_mapping(inode, &bh, vma, vmf); + + out: + if (error == -ENOMEM) + return VM_FAULT_OOM | major; + /* -EBUSY is fine, somebody else faulted on the same PTE */ + if ((error < 0) && (error != -EBUSY)) + return VM_FAULT_SIGBUS | major; + return VM_FAULT_NOPAGE | major; + + unlock_page: + if (page) { + unlock_page(page); + page_cache_release(page); + } + goto out; +} + +/** + * dax_fault - handle a page 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 + * fault handler for DAX files. + */ +int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, + get_block_t get_block) +{ + int result; + struct super_block *sb = file_inode(vma->vm_file)->i_sb; + + if (vmf->flags & FAULT_FLAG_WRITE) { + sb_start_pagefault(sb); + file_update_time(vma->vm_file); + } + result = do_dax_fault(vma, vmf, get_block); + if (vmf->flags & FAULT_FLAG_WRITE) + sb_end_pagefault(sb); + + return result; +} +EXPORT_SYMBOL_GPL(dax_fault); |