ext4 crypto: add ext4_mpage_readpages()
This takes code from fs/mpage.c and optimizes it for ext4. Its primary reason is to allow us to more easily add encryption to ext4's read path in an efficient manner. Signed-off-by: Theodore Ts'o <tytso@mit.edu>hifive-unleashed-5.1
Theodore Ts'o
parent
e12fb97222
commit
f64e02fe9b
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@ -8,7 +8,7 @@ ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
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ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
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ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
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mmp.o indirect.o extents_status.o xattr.o xattr_user.o \
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xattr_trusted.o inline.o
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xattr_trusted.o inline.o readpage.o
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ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o
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ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
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@ -2699,6 +2699,10 @@ static inline void ext4_set_de_type(struct super_block *sb,
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de->file_type = ext4_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
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}
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/* readpages.c */
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extern int ext4_mpage_readpages(struct address_space *mapping,
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struct list_head *pages, struct page *page,
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unsigned nr_pages);
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/* symlink.c */
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extern const struct inode_operations ext4_symlink_inode_operations;
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@ -2820,7 +2820,7 @@ static int ext4_readpage(struct file *file, struct page *page)
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ret = ext4_readpage_inline(inode, page);
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if (ret == -EAGAIN)
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return mpage_readpage(page, ext4_get_block);
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return ext4_mpage_readpages(page->mapping, NULL, page, 1);
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return ret;
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}
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@ -2835,7 +2835,7 @@ ext4_readpages(struct file *file, struct address_space *mapping,
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if (ext4_has_inline_data(inode))
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return 0;
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return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
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return ext4_mpage_readpages(mapping, pages, NULL, nr_pages);
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}
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static void ext4_invalidatepage(struct page *page, unsigned int offset,
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@ -0,0 +1,264 @@
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/*
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* linux/fs/ext4/readpage.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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* Copyright (C) 2015, Google, Inc.
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*
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* This was originally taken from fs/mpage.c
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*
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* The intent is the ext4_mpage_readpages() function here is intended
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* to replace mpage_readpages() in the general case, not just for
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* encrypted files. It has some limitations (see below), where it
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* will fall back to read_block_full_page(), but these limitations
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* should only be hit when page_size != block_size.
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*
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* This will allow us to attach a callback function to support ext4
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* encryption.
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*
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* If anything unusual happens, such as:
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*
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* - encountering a page which has buffers
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* - encountering a page which has a non-hole after a hole
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* - encountering a page with non-contiguous blocks
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*
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* then this code just gives up and calls the buffer_head-based read function.
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* It does handle a page which has holes at the end - that is a common case:
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* the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/mm.h>
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#include <linux/kdev_t.h>
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#include <linux/gfp.h>
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#include <linux/bio.h>
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#include <linux/fs.h>
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#include <linux/buffer_head.h>
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#include <linux/blkdev.h>
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#include <linux/highmem.h>
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#include <linux/prefetch.h>
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#include <linux/mpage.h>
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#include <linux/writeback.h>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
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#include <linux/cleancache.h>
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#include "ext4.h"
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/*
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* I/O completion handler for multipage BIOs.
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*
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* The mpage code never puts partial pages into a BIO (except for end-of-file).
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* If a page does not map to a contiguous run of blocks then it simply falls
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* back to block_read_full_page().
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*
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* Why is this? If a page's completion depends on a number of different BIOs
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* which can complete in any order (or at the same time) then determining the
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* status of that page is hard. See end_buffer_async_read() for the details.
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* There is no point in duplicating all that complexity.
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*/
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static void mpage_end_io(struct bio *bio, int err)
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{
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struct bio_vec *bv;
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int i;
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bio_for_each_segment_all(bv, bio, i) {
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struct page *page = bv->bv_page;
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if (!err) {
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SetPageUptodate(page);
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} else {
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ClearPageUptodate(page);
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SetPageError(page);
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}
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unlock_page(page);
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}
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bio_put(bio);
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}
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int ext4_mpage_readpages(struct address_space *mapping,
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struct list_head *pages, struct page *page,
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unsigned nr_pages)
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{
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struct bio *bio = NULL;
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unsigned page_idx;
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sector_t last_block_in_bio = 0;
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struct inode *inode = mapping->host;
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const unsigned blkbits = inode->i_blkbits;
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const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
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const unsigned blocksize = 1 << blkbits;
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sector_t block_in_file;
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sector_t last_block;
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sector_t last_block_in_file;
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sector_t blocks[MAX_BUF_PER_PAGE];
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unsigned page_block;
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struct block_device *bdev = inode->i_sb->s_bdev;
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int length;
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unsigned relative_block = 0;
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struct ext4_map_blocks map;
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map.m_pblk = 0;
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map.m_lblk = 0;
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map.m_len = 0;
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map.m_flags = 0;
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for (page_idx = 0; nr_pages; page_idx++, nr_pages--) {
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int fully_mapped = 1;
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unsigned first_hole = blocks_per_page;
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prefetchw(&page->flags);
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if (pages) {
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page = list_entry(pages->prev, struct page, lru);
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list_del(&page->lru);
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if (add_to_page_cache_lru(page, mapping,
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page->index, GFP_KERNEL))
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goto next_page;
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}
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if (page_has_buffers(page))
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goto confused;
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block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
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last_block = block_in_file + nr_pages * blocks_per_page;
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last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
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if (last_block > last_block_in_file)
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last_block = last_block_in_file;
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page_block = 0;
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/*
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* Map blocks using the previous result first.
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*/
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if ((map.m_flags & EXT4_MAP_MAPPED) &&
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block_in_file > map.m_lblk &&
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block_in_file < (map.m_lblk + map.m_len)) {
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unsigned map_offset = block_in_file - map.m_lblk;
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unsigned last = map.m_len - map_offset;
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for (relative_block = 0; ; relative_block++) {
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if (relative_block == last) {
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/* needed? */
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map.m_flags &= ~EXT4_MAP_MAPPED;
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break;
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}
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if (page_block == blocks_per_page)
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break;
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blocks[page_block] = map.m_pblk + map_offset +
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relative_block;
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page_block++;
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block_in_file++;
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}
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}
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/*
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* Then do more ext4_map_blocks() calls until we are
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* done with this page.
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*/
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while (page_block < blocks_per_page) {
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if (block_in_file < last_block) {
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map.m_lblk = block_in_file;
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map.m_len = last_block - block_in_file;
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if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
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set_error_page:
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SetPageError(page);
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zero_user_segment(page, 0,
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PAGE_CACHE_SIZE);
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unlock_page(page);
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goto next_page;
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}
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}
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if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
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fully_mapped = 0;
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if (first_hole == blocks_per_page)
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first_hole = page_block;
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page_block++;
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block_in_file++;
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continue;
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}
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if (first_hole != blocks_per_page)
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goto confused; /* hole -> non-hole */
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/* Contiguous blocks? */
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if (page_block && blocks[page_block-1] != map.m_pblk-1)
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goto confused;
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for (relative_block = 0; ; relative_block++) {
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if (relative_block == map.m_len) {
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/* needed? */
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map.m_flags &= ~EXT4_MAP_MAPPED;
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break;
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} else if (page_block == blocks_per_page)
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break;
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blocks[page_block] = map.m_pblk+relative_block;
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page_block++;
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block_in_file++;
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}
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}
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if (first_hole != blocks_per_page) {
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zero_user_segment(page, first_hole << blkbits,
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PAGE_CACHE_SIZE);
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if (first_hole == 0) {
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SetPageUptodate(page);
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unlock_page(page);
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goto next_page;
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}
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} else if (fully_mapped) {
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SetPageMappedToDisk(page);
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}
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if (fully_mapped && blocks_per_page == 1 &&
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!PageUptodate(page) && cleancache_get_page(page) == 0) {
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SetPageUptodate(page);
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goto confused;
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}
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/*
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* This page will go to BIO. Do we need to send this
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* BIO off first?
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*/
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if (bio && (last_block_in_bio != blocks[0] - 1)) {
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submit_and_realloc:
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submit_bio(READ, bio);
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bio = NULL;
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}
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if (bio == NULL) {
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bio = bio_alloc(GFP_KERNEL,
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min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
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if (!bio)
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goto set_error_page;
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bio->bi_bdev = bdev;
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bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
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bio->bi_end_io = mpage_end_io;
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}
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length = first_hole << blkbits;
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if (bio_add_page(bio, page, length, 0) < length)
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goto submit_and_realloc;
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if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
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(relative_block == map.m_len)) ||
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(first_hole != blocks_per_page)) {
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submit_bio(READ, bio);
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bio = NULL;
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} else
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last_block_in_bio = blocks[blocks_per_page - 1];
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goto next_page;
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confused:
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if (bio) {
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submit_bio(READ, bio);
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bio = NULL;
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}
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if (!PageUptodate(page))
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block_read_full_page(page, ext4_get_block);
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else
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unlock_page(page);
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next_page:
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if (pages)
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page_cache_release(page);
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}
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BUG_ON(pages && !list_empty(pages));
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if (bio)
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submit_bio(READ, bio);
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return 0;
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}
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