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![Al Viro](/assets/img/avatar_default.png)
Tetsuo Handa wrote:
"Commit 62a8067a7f
("bio_vec-backed iov_iter") introduced an unnamed
union inside a struct which gcc-4.4.7 cannot handle. Name the unnamed
union as u in order to fix build failure"
Let's do this instead: there is only one place in the entire tree that
steps into this breakage. Anon structs and unions work in older gcc
versions; as the matter of fact, we have those in the tree - see e.g.
struct ieee80211_tx_info in include/net/mac80211.h
What doesn't work is handling their initializers:
struct {
int a;
union {
int b;
char c;
};
} x[2] = {{.a = 1, .c = 'a'}, {.a = 0, .b = 1}};
is the obvious syntax for initializer, perfectly fine for C11 and
handled correctly by gcc-4.7 or later.
Earlier versions, though, break on it - declaration is fine and so's
access to fields (i.e. x[0].c = 'a'; would produce the right code), but
members of the anon structs and unions are not inserted into the right
namespace. Tellingly, those older versions will not barf on struct {int
a; struct {int a;};}; - looks like they just have it hacked up somewhere
around the handling of . and -> instead of doing the right thing.
The easiest way to deal with that crap is to turn initialization of
those fields (in the only place where we have such initializer of
iov_iter) into plain assignment.
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
389 lines
9.5 KiB
C
389 lines
9.5 KiB
C
/*
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* linux/mm/page_io.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Swap reorganised 29.12.95,
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* Asynchronous swapping added 30.12.95. Stephen Tweedie
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* Removed race in async swapping. 14.4.1996. Bruno Haible
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* Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
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* Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
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*/
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#include <linux/mm.h>
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#include <linux/kernel_stat.h>
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#include <linux/gfp.h>
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#include <linux/pagemap.h>
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#include <linux/swap.h>
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#include <linux/bio.h>
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#include <linux/swapops.h>
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#include <linux/buffer_head.h>
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#include <linux/writeback.h>
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#include <linux/frontswap.h>
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#include <linux/aio.h>
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#include <linux/blkdev.h>
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#include <asm/pgtable.h>
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static struct bio *get_swap_bio(gfp_t gfp_flags,
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struct page *page, bio_end_io_t end_io)
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{
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struct bio *bio;
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bio = bio_alloc(gfp_flags, 1);
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if (bio) {
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bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev);
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bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
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bio->bi_io_vec[0].bv_page = page;
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bio->bi_io_vec[0].bv_len = PAGE_SIZE;
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bio->bi_io_vec[0].bv_offset = 0;
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bio->bi_vcnt = 1;
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bio->bi_iter.bi_size = PAGE_SIZE;
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bio->bi_end_io = end_io;
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}
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return bio;
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}
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void end_swap_bio_write(struct bio *bio, int err)
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{
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const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct page *page = bio->bi_io_vec[0].bv_page;
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if (!uptodate) {
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SetPageError(page);
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/*
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* We failed to write the page out to swap-space.
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* Re-dirty the page in order to avoid it being reclaimed.
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* Also print a dire warning that things will go BAD (tm)
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* very quickly.
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*
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* Also clear PG_reclaim to avoid rotate_reclaimable_page()
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*/
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set_page_dirty(page);
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printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
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imajor(bio->bi_bdev->bd_inode),
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iminor(bio->bi_bdev->bd_inode),
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(unsigned long long)bio->bi_iter.bi_sector);
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ClearPageReclaim(page);
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}
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end_page_writeback(page);
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bio_put(bio);
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}
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void end_swap_bio_read(struct bio *bio, int err)
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{
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const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct page *page = bio->bi_io_vec[0].bv_page;
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if (!uptodate) {
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SetPageError(page);
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ClearPageUptodate(page);
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printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
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imajor(bio->bi_bdev->bd_inode),
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iminor(bio->bi_bdev->bd_inode),
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(unsigned long long)bio->bi_iter.bi_sector);
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goto out;
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}
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SetPageUptodate(page);
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/*
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* There is no guarantee that the page is in swap cache - the software
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* suspend code (at least) uses end_swap_bio_read() against a non-
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* swapcache page. So we must check PG_swapcache before proceeding with
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* this optimization.
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*/
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if (likely(PageSwapCache(page))) {
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struct swap_info_struct *sis;
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sis = page_swap_info(page);
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if (sis->flags & SWP_BLKDEV) {
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/*
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* The swap subsystem performs lazy swap slot freeing,
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* expecting that the page will be swapped out again.
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* So we can avoid an unnecessary write if the page
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* isn't redirtied.
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* This is good for real swap storage because we can
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* reduce unnecessary I/O and enhance wear-leveling
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* if an SSD is used as the as swap device.
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* But if in-memory swap device (eg zram) is used,
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* this causes a duplicated copy between uncompressed
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* data in VM-owned memory and compressed data in
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* zram-owned memory. So let's free zram-owned memory
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* and make the VM-owned decompressed page *dirty*,
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* so the page should be swapped out somewhere again if
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* we again wish to reclaim it.
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*/
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struct gendisk *disk = sis->bdev->bd_disk;
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if (disk->fops->swap_slot_free_notify) {
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swp_entry_t entry;
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unsigned long offset;
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entry.val = page_private(page);
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offset = swp_offset(entry);
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SetPageDirty(page);
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disk->fops->swap_slot_free_notify(sis->bdev,
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offset);
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}
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}
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}
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out:
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unlock_page(page);
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bio_put(bio);
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}
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int generic_swapfile_activate(struct swap_info_struct *sis,
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struct file *swap_file,
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sector_t *span)
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{
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struct address_space *mapping = swap_file->f_mapping;
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struct inode *inode = mapping->host;
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unsigned blocks_per_page;
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unsigned long page_no;
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unsigned blkbits;
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sector_t probe_block;
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sector_t last_block;
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sector_t lowest_block = -1;
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sector_t highest_block = 0;
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int nr_extents = 0;
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int ret;
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blkbits = inode->i_blkbits;
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blocks_per_page = PAGE_SIZE >> blkbits;
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/*
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* Map all the blocks into the extent list. This code doesn't try
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* to be very smart.
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*/
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probe_block = 0;
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page_no = 0;
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last_block = i_size_read(inode) >> blkbits;
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while ((probe_block + blocks_per_page) <= last_block &&
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page_no < sis->max) {
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unsigned block_in_page;
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sector_t first_block;
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first_block = bmap(inode, probe_block);
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if (first_block == 0)
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goto bad_bmap;
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/*
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* It must be PAGE_SIZE aligned on-disk
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*/
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if (first_block & (blocks_per_page - 1)) {
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probe_block++;
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goto reprobe;
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}
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for (block_in_page = 1; block_in_page < blocks_per_page;
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block_in_page++) {
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sector_t block;
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block = bmap(inode, probe_block + block_in_page);
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if (block == 0)
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goto bad_bmap;
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if (block != first_block + block_in_page) {
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/* Discontiguity */
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probe_block++;
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goto reprobe;
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}
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}
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first_block >>= (PAGE_SHIFT - blkbits);
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if (page_no) { /* exclude the header page */
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if (first_block < lowest_block)
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lowest_block = first_block;
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if (first_block > highest_block)
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highest_block = first_block;
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}
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/*
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* We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
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*/
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ret = add_swap_extent(sis, page_no, 1, first_block);
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if (ret < 0)
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goto out;
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nr_extents += ret;
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page_no++;
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probe_block += blocks_per_page;
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reprobe:
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continue;
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}
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ret = nr_extents;
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*span = 1 + highest_block - lowest_block;
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if (page_no == 0)
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page_no = 1; /* force Empty message */
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sis->max = page_no;
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sis->pages = page_no - 1;
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sis->highest_bit = page_no - 1;
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out:
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return ret;
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bad_bmap:
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printk(KERN_ERR "swapon: swapfile has holes\n");
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ret = -EINVAL;
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goto out;
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}
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/*
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* We may have stale swap cache pages in memory: notice
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* them here and get rid of the unnecessary final write.
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*/
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int swap_writepage(struct page *page, struct writeback_control *wbc)
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{
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int ret = 0;
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if (try_to_free_swap(page)) {
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unlock_page(page);
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goto out;
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}
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if (frontswap_store(page) == 0) {
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set_page_writeback(page);
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unlock_page(page);
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end_page_writeback(page);
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goto out;
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}
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ret = __swap_writepage(page, wbc, end_swap_bio_write);
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out:
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return ret;
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}
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static sector_t swap_page_sector(struct page *page)
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{
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return (sector_t)__page_file_index(page) << (PAGE_CACHE_SHIFT - 9);
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}
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int __swap_writepage(struct page *page, struct writeback_control *wbc,
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void (*end_write_func)(struct bio *, int))
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{
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struct bio *bio;
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int ret, rw = WRITE;
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struct swap_info_struct *sis = page_swap_info(page);
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if (sis->flags & SWP_FILE) {
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struct kiocb kiocb;
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struct file *swap_file = sis->swap_file;
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struct address_space *mapping = swap_file->f_mapping;
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struct bio_vec bv = {
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.bv_page = page,
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.bv_len = PAGE_SIZE,
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.bv_offset = 0
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};
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struct iov_iter from = {
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.type = ITER_BVEC | WRITE,
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.count = PAGE_SIZE,
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.iov_offset = 0,
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.nr_segs = 1,
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};
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from.bvec = &bv; /* older gcc versions are broken */
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init_sync_kiocb(&kiocb, swap_file);
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kiocb.ki_pos = page_file_offset(page);
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kiocb.ki_nbytes = PAGE_SIZE;
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set_page_writeback(page);
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unlock_page(page);
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ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
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&kiocb, &from,
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kiocb.ki_pos);
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if (ret == PAGE_SIZE) {
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count_vm_event(PSWPOUT);
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ret = 0;
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} else {
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/*
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* In the case of swap-over-nfs, this can be a
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* temporary failure if the system has limited
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* memory for allocating transmit buffers.
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* Mark the page dirty and avoid
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* rotate_reclaimable_page but rate-limit the
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* messages but do not flag PageError like
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* the normal direct-to-bio case as it could
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* be temporary.
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*/
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set_page_dirty(page);
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ClearPageReclaim(page);
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pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
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page_file_offset(page));
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}
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end_page_writeback(page);
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return ret;
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}
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ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
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if (!ret) {
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count_vm_event(PSWPOUT);
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return 0;
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}
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ret = 0;
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bio = get_swap_bio(GFP_NOIO, page, end_write_func);
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if (bio == NULL) {
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set_page_dirty(page);
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unlock_page(page);
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ret = -ENOMEM;
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goto out;
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}
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if (wbc->sync_mode == WB_SYNC_ALL)
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rw |= REQ_SYNC;
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count_vm_event(PSWPOUT);
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set_page_writeback(page);
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unlock_page(page);
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submit_bio(rw, bio);
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out:
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return ret;
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}
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int swap_readpage(struct page *page)
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{
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struct bio *bio;
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int ret = 0;
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struct swap_info_struct *sis = page_swap_info(page);
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(PageUptodate(page), page);
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if (frontswap_load(page) == 0) {
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SetPageUptodate(page);
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unlock_page(page);
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goto out;
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}
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if (sis->flags & SWP_FILE) {
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struct file *swap_file = sis->swap_file;
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struct address_space *mapping = swap_file->f_mapping;
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ret = mapping->a_ops->readpage(swap_file, page);
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if (!ret)
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count_vm_event(PSWPIN);
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return ret;
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}
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ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
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if (!ret) {
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count_vm_event(PSWPIN);
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return 0;
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}
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ret = 0;
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bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
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if (bio == NULL) {
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unlock_page(page);
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ret = -ENOMEM;
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goto out;
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}
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count_vm_event(PSWPIN);
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submit_bio(READ, bio);
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out:
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return ret;
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}
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int swap_set_page_dirty(struct page *page)
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{
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struct swap_info_struct *sis = page_swap_info(page);
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if (sis->flags & SWP_FILE) {
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struct address_space *mapping = sis->swap_file->f_mapping;
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return mapping->a_ops->set_page_dirty(page);
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} else {
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return __set_page_dirty_no_writeback(page);
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}
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}
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