buffered-io.c
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2010 Red Hat, Inc.
* Copyright (C) 2016-2019 Christoph Hellwig.
*/
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include <linux/writeback.h>
#include <linux/list_sort.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/sched/signal.h>
#include <linux/migrate.h>
#include "trace.h"
#include "../internal.h"
#define IOEND_BATCH_SIZE 4096
/*
* Structure allocated for each folio when block size < folio size
* to track sub-folio uptodate status and I/O completions.
*/
struct iomap_page {
atomic_t read_bytes_pending;
atomic_t write_bytes_pending;
spinlock_t uptodate_lock;
unsigned long uptodate[];
};
static inline struct iomap_page *to_iomap_page(struct folio *folio)
{
if (folio_test_private(folio))
return folio_get_private(folio);
return NULL;
}
static struct bio_set iomap_ioend_bioset;
static struct iomap_page *
iomap_page_create(struct inode *inode, struct folio *folio)
{
struct iomap_page *iop = to_iomap_page(folio);
unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
if (iop || nr_blocks <= 1)
return iop;
iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
GFP_NOFS | __GFP_NOFAIL);
spin_lock_init(&iop->uptodate_lock);
if (folio_test_uptodate(folio))
bitmap_fill(iop->uptodate, nr_blocks);
folio_attach_private(folio, iop);
return iop;
}
static void iomap_page_release(struct folio *folio)
{
struct iomap_page *iop = folio_detach_private(folio);
struct inode *inode = folio->mapping->host;
unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
if (!iop)
return;
WARN_ON_ONCE(atomic_read(&iop->read_bytes_pending));
WARN_ON_ONCE(atomic_read(&iop->write_bytes_pending));
WARN_ON_ONCE(bitmap_full(iop->uptodate, nr_blocks) !=
folio_test_uptodate(folio));
kfree(iop);
}
/*
* Calculate the range inside the folio that we actually need to read.
*/
static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
loff_t *pos, loff_t length, size_t *offp, size_t *lenp)
{
struct iomap_page *iop = to_iomap_page(folio);
loff_t orig_pos = *pos;
loff_t isize = i_size_read(inode);
unsigned block_bits = inode->i_blkbits;
unsigned block_size = (1 << block_bits);
size_t poff = offset_in_folio(folio, *pos);
size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
unsigned first = poff >> block_bits;
unsigned last = (poff + plen - 1) >> block_bits;
/*
* If the block size is smaller than the page size, we need to check the
* per-block uptodate status and adjust the offset and length if needed
* to avoid reading in already uptodate ranges.
*/
if (iop) {
unsigned int i;
/* move forward for each leading block marked uptodate */
for (i = first; i <= last; i++) {
if (!test_bit(i, iop->uptodate))
break;
*pos += block_size;
poff += block_size;
plen -= block_size;
first++;
}
/* truncate len if we find any trailing uptodate block(s) */
for ( ; i <= last; i++) {
if (test_bit(i, iop->uptodate)) {
plen -= (last - i + 1) * block_size;
last = i - 1;
break;
}
}
}
/*
* If the extent spans the block that contains the i_size, we need to
* handle both halves separately so that we properly zero data in the
* page cache for blocks that are entirely outside of i_size.
*/
if (orig_pos <= isize && orig_pos + length > isize) {
unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
if (first <= end && last > end)
plen -= (last - end) * block_size;
}
*offp = poff;
*lenp = plen;
}
static void iomap_iop_set_range_uptodate(struct folio *folio,
struct iomap_page *iop, size_t off, size_t len)
{
struct inode *inode = folio->mapping->host;
unsigned first = off >> inode->i_blkbits;
unsigned last = (off + len - 1) >> inode->i_blkbits;
unsigned long flags;
spin_lock_irqsave(&iop->uptodate_lock, flags);
bitmap_set(iop->uptodate, first, last - first + 1);
if (bitmap_full(iop->uptodate, i_blocks_per_folio(inode, folio)))
folio_mark_uptodate(folio);
spin_unlock_irqrestore(&iop->uptodate_lock, flags);
}
static void iomap_set_range_uptodate(struct folio *folio,
struct iomap_page *iop, size_t off, size_t len)
{
if (folio_test_error(folio))
return;
if (iop)
iomap_iop_set_range_uptodate(folio, iop, off, len);
else
folio_mark_uptodate(folio);
}
static void iomap_finish_folio_read(struct folio *folio, size_t offset,
size_t len, int error)
{
struct iomap_page *iop = to_iomap_page(folio);
if (unlikely(error)) {
folio_clear_uptodate(folio);
folio_set_error(folio);
} else {
iomap_set_range_uptodate(folio, iop, offset, len);
}
if (!iop || atomic_sub_and_test(len, &iop->read_bytes_pending))
folio_unlock(folio);
}
static void iomap_read_end_io(struct bio *bio)
{
int error = blk_status_to_errno(bio->bi_status);
struct folio_iter fi;
bio_for_each_folio_all(fi, bio)
iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
bio_put(bio);
}
struct iomap_readpage_ctx {
struct folio *cur_folio;
bool cur_folio_in_bio;
struct bio *bio;
struct readahead_control *rac;
};
/**
* iomap_read_inline_data - copy inline data into the page cache
* @iter: iteration structure
* @folio: folio to copy to
*
* Copy the inline data in @iter into @folio and zero out the rest of the folio.
* Only a single IOMAP_INLINE extent is allowed at the end of each file.
* Returns zero for success to complete the read, or the usual negative errno.
*/
static int iomap_read_inline_data(const struct iomap_iter *iter,
struct folio *folio)
{
struct iomap_page *iop;
const struct iomap *iomap = iomap_iter_srcmap(iter);
size_t size = i_size_read(iter->inode) - iomap->offset;
size_t poff = offset_in_page(iomap->offset);
size_t offset = offset_in_folio(folio, iomap->offset);
void *addr;
if (folio_test_uptodate(folio))
return 0;
if (WARN_ON_ONCE(size > PAGE_SIZE - poff))
return -EIO;
if (WARN_ON_ONCE(size > PAGE_SIZE -
offset_in_page(iomap->inline_data)))
return -EIO;
if (WARN_ON_ONCE(size > iomap->length))
return -EIO;
if (offset > 0)
iop = iomap_page_create(iter->inode, folio);
else
iop = to_iomap_page(folio);
addr = kmap_local_folio(folio, offset);
memcpy(addr, iomap->inline_data, size);
memset(addr + size, 0, PAGE_SIZE - poff - size);
kunmap_local(addr);
iomap_set_range_uptodate(folio, iop, offset, PAGE_SIZE - poff);
return 0;
}
static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
loff_t pos)
{
const struct iomap *srcmap = iomap_iter_srcmap(iter);
return srcmap->type != IOMAP_MAPPED ||
(srcmap->flags & IOMAP_F_NEW) ||
pos >= i_size_read(iter->inode);
}
static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
struct iomap_readpage_ctx *ctx, loff_t offset)
{
const struct iomap *iomap = &iter->iomap;
loff_t pos = iter->pos + offset;
loff_t length = iomap_length(iter) - offset;
struct folio *folio = ctx->cur_folio;
struct iomap_page *iop;
loff_t orig_pos = pos;
size_t poff, plen;
sector_t sector;
if (iomap->type == IOMAP_INLINE)
return iomap_read_inline_data(iter, folio);
/* zero post-eof blocks as the page may be mapped */
iop = iomap_page_create(iter->inode, folio);
iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
if (plen == 0)
goto done;
if (iomap_block_needs_zeroing(iter, pos)) {
folio_zero_range(folio, poff, plen);
iomap_set_range_uptodate(folio, iop, poff, plen);
goto done;
}
ctx->cur_folio_in_bio = true;
if (iop)
atomic_add(plen, &iop->read_bytes_pending);
sector = iomap_sector(iomap, pos);
if (!ctx->bio ||
bio_end_sector(ctx->bio) != sector ||
!bio_add_folio(ctx->bio, folio, plen, poff)) {
gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
gfp_t orig_gfp = gfp;
unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);
if (ctx->bio)
submit_bio(ctx->bio);
if (ctx->rac) /* same as readahead_gfp_mask */
gfp |= __GFP_NORETRY | __GFP_NOWARN;
ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
REQ_OP_READ, gfp);
/*
* If the bio_alloc fails, try it again for a single page to
* avoid having to deal with partial page reads. This emulates
* what do_mpage_readpage does.
*/
if (!ctx->bio) {
ctx->bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ,
orig_gfp);
}
if (ctx->rac)
ctx->bio->bi_opf |= REQ_RAHEAD;
ctx->bio->bi_iter.bi_sector = sector;
ctx->bio->bi_end_io = iomap_read_end_io;
bio_add_folio(ctx->bio, folio, plen, poff);
}
done:
/*
* Move the caller beyond our range so that it keeps making progress.
* For that, we have to include any leading non-uptodate ranges, but
* we can skip trailing ones as they will be handled in the next
* iteration.
*/
return pos - orig_pos + plen;
}
int
iomap_readpage(struct page *page, const struct iomap_ops *ops)
{
struct folio *folio = page_folio(page);
struct iomap_iter iter = {
.inode = folio->mapping->host,
.pos = folio_pos(folio),
.len = folio_size(folio),
};
struct iomap_readpage_ctx ctx = {
.cur_folio = folio,
};
int ret;
trace_iomap_readpage(iter.inode, 1);
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_readpage_iter(&iter, &ctx, 0);
if (ret < 0)
folio_set_error(folio);
if (ctx.bio) {
submit_bio(ctx.bio);
WARN_ON_ONCE(!ctx.cur_folio_in_bio);
} else {
WARN_ON_ONCE(ctx.cur_folio_in_bio);
folio_unlock(folio);
}
/*
* Just like mpage_readahead and block_read_full_page, we always
* return 0 and just mark the page as PageError on errors. This
* should be cleaned up throughout the stack eventually.
*/
return 0;
}
EXPORT_SYMBOL_GPL(iomap_readpage);
static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
struct iomap_readpage_ctx *ctx)
{
loff_t length = iomap_length(iter);
loff_t done, ret;
for (done = 0; done < length; done += ret) {
if (ctx->cur_folio &&
offset_in_folio(ctx->cur_folio, iter->pos + done) == 0) {
if (!ctx->cur_folio_in_bio)
folio_unlock(ctx->cur_folio);
ctx->cur_folio = NULL;
}
if (!ctx->cur_folio) {
ctx->cur_folio = readahead_folio(ctx->rac);
ctx->cur_folio_in_bio = false;
}
ret = iomap_readpage_iter(iter, ctx, done);
if (ret <= 0)
return ret;
}
return done;
}
/**
* iomap_readahead - Attempt to read pages from a file.
* @rac: Describes the pages to be read.
* @ops: The operations vector for the filesystem.
*
* This function is for filesystems to call to implement their readahead
* address_space operation.
*
* Context: The @ops callbacks may submit I/O (eg to read the addresses of
* blocks from disc), and may wait for it. The caller may be trying to
* access a different page, and so sleeping excessively should be avoided.
* It may allocate memory, but should avoid costly allocations. This
* function is called with memalloc_nofs set, so allocations will not cause
* the filesystem to be reentered.
*/
void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
{
struct iomap_iter iter = {
.inode = rac->mapping->host,
.pos = readahead_pos(rac),
.len = readahead_length(rac),
};
struct iomap_readpage_ctx ctx = {
.rac = rac,
};
trace_iomap_readahead(rac->mapping->host, readahead_count(rac));
while (iomap_iter(&iter, ops) > 0)
iter.processed = iomap_readahead_iter(&iter, &ctx);
if (ctx.bio)
submit_bio(ctx.bio);
if (ctx.cur_folio) {
if (!ctx.cur_folio_in_bio)
folio_unlock(ctx.cur_folio);
}
}
EXPORT_SYMBOL_GPL(iomap_readahead);
/*
* iomap_is_partially_uptodate checks whether blocks within a folio are
* uptodate or not.
*
* Returns true if all blocks which correspond to the specified part
* of the folio are uptodate.
*/
bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
{
struct iomap_page *iop = to_iomap_page(folio);
struct inode *inode = folio->mapping->host;
unsigned first, last, i;
if (!iop)
return false;
/* Caller's range may extend past the end of this folio */
count = min(folio_size(folio) - from, count);
/* First and last blocks in range within folio */
first = from >> inode->i_blkbits;
last = (from + count - 1) >> inode->i_blkbits;
for (i = first; i <= last; i++)
if (!test_bit(i, iop->uptodate))
return false;
return true;
}
EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
int
iomap_releasepage(struct page *page, gfp_t gfp_mask)
{
struct folio *folio = page_folio(page);
trace_iomap_releasepage(folio->mapping->host, folio_pos(folio),
folio_size(folio));
/*
* mm accommodates an old ext3 case where clean pages might not have had
* the dirty bit cleared. Thus, it can send actual dirty pages to
* ->releasepage() via shrink_active_list(); skip those here.
*/
if (folio_test_dirty(folio) || folio_test_writeback(folio))
return 0;
iomap_page_release(folio);
return 1;
}
EXPORT_SYMBOL_GPL(iomap_releasepage);
void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
{
trace_iomap_invalidate_folio(folio->mapping->host,
folio_pos(folio) + offset, len);
/*
* If we're invalidating the entire folio, clear the dirty state
* from it and release it to avoid unnecessary buildup of the LRU.
*/
if (offset == 0 && len == folio_size(folio)) {
WARN_ON_ONCE(folio_test_writeback(folio));
folio_cancel_dirty(folio);
iomap_page_release(folio);
} else if (folio_test_large(folio)) {
/* Must release the iop so the page can be split */
WARN_ON_ONCE(!folio_test_uptodate(folio) &&
folio_test_dirty(folio));
iomap_page_release(folio);
}
}
EXPORT_SYMBOL_GPL(iomap_invalidate_folio);
#ifdef CONFIG_MIGRATION
int
iomap_migrate_page(struct address_space *mapping, struct page *newpage,
struct page *page, enum migrate_mode mode)
{
struct folio *folio = page_folio(page);
struct folio *newfolio = page_folio(newpage);
int ret;
ret = folio_migrate_mapping(mapping, newfolio, folio, 0);
if (ret != MIGRATEPAGE_SUCCESS)
return ret;
if (folio_test_private(folio))
folio_attach_private(newfolio, folio_detach_private(folio));
if (mode != MIGRATE_SYNC_NO_COPY)
folio_migrate_copy(newfolio, folio);
else
folio_migrate_flags(newfolio, folio);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL_GPL(iomap_migrate_page);
#endif /* CONFIG_MIGRATION */
static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
loff_t i_size = i_size_read(inode);
/*
* Only truncate newly allocated pages beyoned EOF, even if the
* write started inside the existing inode size.
*/
if (pos + len > i_size)
truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}
static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
size_t poff, size_t plen, const struct iomap *iomap)
{
struct bio_vec bvec;
struct bio bio;
bio_init(&bio, iomap->bdev, &bvec, 1, REQ_OP_READ);
bio.bi_iter.bi_sector = iomap_sector(iomap, block_start);
bio_add_folio(&bio, folio, plen, poff);
return submit_bio_wait(&bio);
}
static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
size_t len, struct folio *folio)
{
const struct iomap *srcmap = iomap_iter_srcmap(iter);
struct iomap_page *iop = iomap_page_create(iter->inode, folio);
loff_t block_size = i_blocksize(iter->inode);
loff_t block_start = round_down(pos, block_size);
loff_t block_end = round_up(pos + len, block_size);
size_t from = offset_in_folio(folio, pos), to = from + len;
size_t poff, plen;
if (folio_test_uptodate(folio))
return 0;
folio_clear_error(folio);
do {
iomap_adjust_read_range(iter->inode, folio, &block_start,
block_end - block_start, &poff, &plen);
if (plen == 0)
break;
if (!(iter->flags & IOMAP_UNSHARE) &&
(from <= poff || from >= poff + plen) &&
(to <= poff || to >= poff + plen))
continue;
if (iomap_block_needs_zeroing(iter, block_start)) {
if (WARN_ON_ONCE(iter->flags & IOMAP_UNSHARE))
return -EIO;
folio_zero_segments(folio, poff, from, to, poff + plen);
} else {
int status = iomap_read_folio_sync(block_start, folio,
poff, plen, srcmap);
if (status)
return status;
}
iomap_set_range_uptodate(folio, iop, poff, plen);
} while ((block_start += plen) < block_end);
return 0;
}
static int iomap_write_begin_inline(const struct iomap_iter *iter,
struct folio *folio)
{
/* needs more work for the tailpacking case; disable for now */
if (WARN_ON_ONCE(iomap_iter_srcmap(iter)->offset != 0))
return -EIO;
return iomap_read_inline_data(iter, folio);
}
static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
size_t len, struct folio **foliop)
{
const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
const struct iomap *srcmap = iomap_iter_srcmap(iter);
struct folio *folio;
unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
int status = 0;
BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
if (srcmap != &iter->iomap)
BUG_ON(pos + len > srcmap->offset + srcmap->length);
if (fatal_signal_pending(current))
return -EINTR;
if (!mapping_large_folio_support(iter->inode->i_mapping))
len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
if (page_ops && page_ops->page_prepare) {
status = page_ops->page_prepare(iter->inode, pos, len);
if (status)
return status;
}
folio = __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
fgp, mapping_gfp_mask(iter->inode->i_mapping));
if (!folio) {
status = -ENOMEM;
goto out_no_page;
}
if (pos + len > folio_pos(folio) + folio_size(folio))
len = folio_pos(folio) + folio_size(folio) - pos;
if (srcmap->type == IOMAP_INLINE)
status = iomap_write_begin_inline(iter, folio);
else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
status = __block_write_begin_int(folio, pos, len, NULL, srcmap);
else
status = __iomap_write_begin(iter, pos, len, folio);
if (unlikely(status))
goto out_unlock;
*foliop = folio;
return 0;
out_unlock:
folio_unlock(folio);
folio_put(folio);
iomap_write_failed(iter->inode, pos, len);
out_no_page:
if (page_ops && page_ops->page_done)
page_ops->page_done(iter->inode, pos, 0, NULL);
return status;
}
static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
size_t copied, struct folio *folio)
{
struct iomap_page *iop = to_iomap_page(folio);
flush_dcache_folio(folio);
/*
* The blocks that were entirely written will now be uptodate, so we
* don't have to worry about a readpage reading them and overwriting a
* partial write. However, if we've encountered a short write and only
* partially written into a block, it will not be marked uptodate, so a
* readpage might come in and destroy our partial write.
*
* Do the simplest thing and just treat any short write to a
* non-uptodate page as a zero-length write, and force the caller to
* redo the whole thing.
*/
if (unlikely(copied < len && !folio_test_uptodate(folio)))
return 0;
iomap_set_range_uptodate(folio, iop, offset_in_folio(folio, pos), len);
filemap_dirty_folio(inode->i_mapping, folio);
return copied;
}
static size_t iomap_write_end_inline(const struct iomap_iter *iter,
struct folio *folio, loff_t pos, size_t copied)
{
const struct iomap *iomap = &iter->iomap;
void *addr;
WARN_ON_ONCE(!folio_test_uptodate(folio));
BUG_ON(!iomap_inline_data_valid(iomap));
flush_dcache_folio(folio);
addr = kmap_local_folio(folio, pos);
memcpy(iomap_inline_data(iomap, pos), addr, copied);
kunmap_local(addr);
mark_inode_dirty(iter->inode);
return copied;
}
/* Returns the number of bytes copied. May be 0. Cannot be an errno. */
static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
size_t copied, struct folio *folio)
{
const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
const struct iomap *srcmap = iomap_iter_srcmap(iter);
loff_t old_size = iter->inode->i_size;
size_t ret;
if (srcmap->type == IOMAP_INLINE) {
ret = iomap_write_end_inline(iter, folio, pos, copied);
} else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
ret = block_write_end(NULL, iter->inode->i_mapping, pos, len,
copied, &folio->page, NULL);
} else {
ret = __iomap_write_end(iter->inode, pos, len, copied, folio);
}
/*
* Update the in-memory inode size after copying the data into the page
* cache. It's up to the file system to write the updated size to disk,
* preferably after I/O completion so that no stale data is exposed.
*/
if (pos + ret > old_size) {
i_size_write(iter->inode, pos + ret);
iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
}
folio_unlock(folio);
if (old_size < pos)
pagecache_isize_extended(iter->inode, old_size, pos);
if (page_ops && page_ops->page_done)
page_ops->page_done(iter->inode, pos, ret, &folio->page);
folio_put(folio);
if (ret < len)
iomap_write_failed(iter->inode, pos, len);
return ret;
}
static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
{
loff_t length = iomap_length(iter);
loff_t pos = iter->pos;
ssize_t written = 0;
long status = 0;
do {
struct folio *folio;
struct page *page;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
offset = offset_in_page(pos);
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_count(i));
again:
if (bytes > length)
bytes = length;
/*
* Bring in the user page that we'll copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*/
if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
status = -EFAULT;
break;
}
status = iomap_write_begin(iter, pos, bytes, &folio);
if (unlikely(status))
break;
page = folio_file_page(folio, pos >> PAGE_SHIFT);
if (mapping_writably_mapped(iter->inode->i_mapping))
flush_dcache_page(page);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
status = iomap_write_end(iter, pos, bytes, copied, folio);
if (unlikely(copied != status))
iov_iter_revert(i, copied - status);
cond_resched();
if (unlikely(status == 0)) {
/*
* A short copy made iomap_write_end() reject the
* thing entirely. Might be memory poisoning
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
if (copied)
bytes = copied;
goto again;
}
pos += status;
written += status;
length -= status;
balance_dirty_pages_ratelimited(iter->inode->i_mapping);
} while (iov_iter_count(i) && length);
return written ? written : status;
}
ssize_t
iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
const struct iomap_ops *ops)
{
struct iomap_iter iter = {
.inode = iocb->ki_filp->f_mapping->host,
.pos = iocb->ki_pos,
.len = iov_iter_count(i),
.flags = IOMAP_WRITE,
};
int ret;
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_write_iter(&iter, i);
if (iter.pos == iocb->ki_pos)
return ret;
return iter.pos - iocb->ki_pos;
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
static loff_t iomap_unshare_iter(struct iomap_iter *iter)
{
struct iomap *iomap = &iter->iomap;
const struct iomap *srcmap = iomap_iter_srcmap(iter);
loff_t pos = iter->pos;
loff_t length = iomap_length(iter);
long status = 0;
loff_t written = 0;
/* don't bother with blocks that are not shared to start with */
if (!(iomap->flags & IOMAP_F_SHARED))
return length;
/* don't bother with holes or unwritten extents */
if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return length;
do {
unsigned long offset = offset_in_page(pos);
unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
struct folio *folio;
status = iomap_write_begin(iter, pos, bytes, &folio);
if (unlikely(status))
return status;
status = iomap_write_end(iter, pos, bytes, bytes, folio);
if (WARN_ON_ONCE(status == 0))
return -EIO;
cond_resched();
pos += status;
written += status;
length -= status;
balance_dirty_pages_ratelimited(iter->inode->i_mapping);
} while (length);
return written;
}
int
iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
const struct iomap_ops *ops)
{
struct iomap_iter iter = {
.inode = inode,
.pos = pos,
.len = len,
.flags = IOMAP_WRITE | IOMAP_UNSHARE,
};
int ret;
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_unshare_iter(&iter);
return ret;
}
EXPORT_SYMBOL_GPL(iomap_file_unshare);
static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
{
const struct iomap *srcmap = iomap_iter_srcmap(iter);
loff_t pos = iter->pos;
loff_t length = iomap_length(iter);
loff_t written = 0;
/* already zeroed? we're done. */
if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return length;
do {
struct folio *folio;
int status;
size_t offset;
size_t bytes = min_t(u64, SIZE_MAX, length);
status = iomap_write_begin(iter, pos, bytes, &folio);
if (status)
return status;
offset = offset_in_folio(folio, pos);
if (bytes > folio_size(folio) - offset)
bytes = folio_size(folio) - offset;
folio_zero_range(folio, offset, bytes);
folio_mark_accessed(folio);
bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
if (WARN_ON_ONCE(bytes == 0))
return -EIO;
pos += bytes;
length -= bytes;
written += bytes;
if (did_zero)
*did_zero = true;
} while (length > 0);
return written;
}
int
iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
const struct iomap_ops *ops)
{
struct iomap_iter iter = {
.inode = inode,
.pos = pos,
.len = len,
.flags = IOMAP_ZERO,
};
int ret;
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_zero_iter(&iter, did_zero);
return ret;
}
EXPORT_SYMBOL_GPL(iomap_zero_range);
int
iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
const struct iomap_ops *ops)
{
unsigned int blocksize = i_blocksize(inode);
unsigned int off = pos & (blocksize - 1);
/* Block boundary? Nothing to do */
if (!off)
return 0;
return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
}
EXPORT_SYMBOL_GPL(iomap_truncate_page);
static loff_t iomap_folio_mkwrite_iter(struct iomap_iter *iter,
struct folio *folio)
{
loff_t length = iomap_length(iter);
int ret;
if (iter->iomap.flags & IOMAP_F_BUFFER_HEAD) {
ret = __block_write_begin_int(folio, iter->pos, length, NULL,
&iter->iomap);
if (ret)
return ret;
block_commit_write(&folio->page, 0, length);
} else {
WARN_ON_ONCE(!folio_test_uptodate(folio));
folio_mark_dirty(folio);
}
return length;
}
vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
{
struct iomap_iter iter = {
.inode = file_inode(vmf->vma->vm_file),
.flags = IOMAP_WRITE | IOMAP_FAULT,
};
struct folio *folio = page_folio(vmf->page);
ssize_t ret;
folio_lock(folio);
ret = folio_mkwrite_check_truncate(folio, iter.inode);
if (ret < 0)
goto out_unlock;
iter.pos = folio_pos(folio);
iter.len = ret;
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_folio_mkwrite_iter(&iter, folio);
if (ret < 0)
goto out_unlock;
folio_wait_stable(folio);
return VM_FAULT_LOCKED;
out_unlock:
folio_unlock(folio);
return block_page_mkwrite_return(ret);
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
size_t len, int error)
{
struct iomap_page *iop = to_iomap_page(folio);
if (error) {
folio_set_error(folio);
mapping_set_error(inode->i_mapping, error);
}
WARN_ON_ONCE(i_blocks_per_folio(inode, folio) > 1 && !iop);
WARN_ON_ONCE(iop && atomic_read(&iop->write_bytes_pending) <= 0);
if (!iop || atomic_sub_and_test(len, &iop->write_bytes_pending))
folio_end_writeback(folio);
}
/*
* We're now finished for good with this ioend structure. Update the page
* state, release holds on bios, and finally free up memory. Do not use the
* ioend after this.
*/
static u32
iomap_finish_ioend(struct iomap_ioend *ioend, int error)
{
struct inode *inode = ioend->io_inode;
struct bio *bio = &ioend->io_inline_bio;
struct bio *last = ioend->io_bio, *next;
u64 start = bio->bi_iter.bi_sector;
loff_t offset = ioend->io_offset;
bool quiet = bio_flagged(bio, BIO_QUIET);
u32 folio_count = 0;
for (bio = &ioend->io_inline_bio; bio; bio = next) {
struct folio_iter fi;
/*
* For the last bio, bi_private points to the ioend, so we
* need to explicitly end the iteration here.
*/
if (bio == last)
next = NULL;
else
next = bio->bi_private;
/* walk all folios in bio, ending page IO on them */
bio_for_each_folio_all(fi, bio) {
iomap_finish_folio_write(inode, fi.folio, fi.length,
error);
folio_count++;
}
bio_put(bio);
}
/* The ioend has been freed by bio_put() */
if (unlikely(error && !quiet)) {
printk_ratelimited(KERN_ERR
"%s: writeback error on inode %lu, offset %lld, sector %llu",
inode->i_sb->s_id, inode->i_ino, offset, start);
}
return folio_count;
}
/*
* Ioend completion routine for merged bios. This can only be called from task
* contexts as merged ioends can be of unbound length. Hence we have to break up
* the writeback completions into manageable chunks to avoid long scheduler
* holdoffs. We aim to keep scheduler holdoffs down below 10ms so that we get
* good batch processing throughput without creating adverse scheduler latency
* conditions.
*/
void
iomap_finish_ioends(struct iomap_ioend *ioend, int error)
{
struct list_head tmp;
u32 completions;
might_sleep();
list_replace_init(&ioend->io_list, &tmp);
completions = iomap_finish_ioend(ioend, error);
while (!list_empty(&tmp)) {
if (completions > IOEND_BATCH_SIZE * 8) {
cond_resched();
completions = 0;
}
ioend = list_first_entry(&tmp, struct iomap_ioend, io_list);
list_del_init(&ioend->io_list);
completions += iomap_finish_ioend(ioend, error);
}
}
EXPORT_SYMBOL_GPL(iomap_finish_ioends);
/*
* We can merge two adjacent ioends if they have the same set of work to do.
*/
static bool
iomap_ioend_can_merge(struct iomap_ioend *ioend, struct iomap_ioend *next)
{
if (ioend->io_bio->bi_status != next->io_bio->bi_status)
return false;
if ((ioend->io_flags & IOMAP_F_SHARED) ^
(next->io_flags & IOMAP_F_SHARED))
return false;
if ((ioend->io_type == IOMAP_UNWRITTEN) ^
(next->io_type == IOMAP_UNWRITTEN))
return false;
if (ioend->io_offset + ioend->io_size != next->io_offset)
return false;
/*
* Do not merge physically discontiguous ioends. The filesystem
* completion functions will have to iterate the physical
* discontiguities even if we merge the ioends at a logical level, so
* we don't gain anything by merging physical discontiguities here.
*
* We cannot use bio->bi_iter.bi_sector here as it is modified during
* submission so does not point to the start sector of the bio at
* completion.
*/
if (ioend->io_sector + (ioend->io_size >> 9) != next->io_sector)
return false;
return true;
}
void
iomap_ioend_try_merge(struct iomap_ioend *ioend, struct list_head *more_ioends)
{
struct iomap_ioend *next;
INIT_LIST_HEAD(&ioend->io_list);
while ((next = list_first_entry_or_null(more_ioends, struct iomap_ioend,
io_list))) {
if (!iomap_ioend_can_merge(ioend, next))
break;
list_move_tail(&next->io_list, &ioend->io_list);
ioend->io_size += next->io_size;
}
}
EXPORT_SYMBOL_GPL(iomap_ioend_try_merge);
static int
iomap_ioend_compare(void *priv, const struct list_head *a,
const struct list_head *b)
{
struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list);
struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list);
if (ia->io_offset < ib->io_offset)
return -1;
if (ia->io_offset > ib->io_offset)
return 1;
return 0;
}
void
iomap_sort_ioends(struct list_head *ioend_list)
{
list_sort(NULL, ioend_list, iomap_ioend_compare);
}
EXPORT_SYMBOL_GPL(iomap_sort_ioends);
static void iomap_writepage_end_bio(struct bio *bio)
{
struct iomap_ioend *ioend = bio->bi_private;
iomap_finish_ioend(ioend, blk_status_to_errno(bio->bi_status));
}
/*
* Submit the final bio for an ioend.
*
* If @error is non-zero, it means that we have a situation where some part of
* the submission process has failed after we've marked pages for writeback
* and unlocked them. In this situation, we need to fail the bio instead of
* submitting it. This typically only happens on a filesystem shutdown.
*/
static int
iomap_submit_ioend(struct iomap_writepage_ctx *wpc, struct iomap_ioend *ioend,
int error)
{
ioend->io_bio->bi_private = ioend;
ioend->io_bio->bi_end_io = iomap_writepage_end_bio;
if (wpc->ops->prepare_ioend)
error = wpc->ops->prepare_ioend(ioend, error);
if (error) {
/*
* If we're failing the IO now, just mark the ioend with an
* error and finish it. This will run IO completion immediately
* as there is only one reference to the ioend at this point in
* time.
*/
ioend->io_bio->bi_status = errno_to_blk_status(error);
bio_endio(ioend->io_bio);
return error;
}
submit_bio(ioend->io_bio);
return 0;
}
static struct iomap_ioend *
iomap_alloc_ioend(struct inode *inode, struct iomap_writepage_ctx *wpc,
loff_t offset, sector_t sector, struct writeback_control *wbc)
{
struct iomap_ioend *ioend;
struct bio *bio;
bio = bio_alloc_bioset(wpc->iomap.bdev, BIO_MAX_VECS,
REQ_OP_WRITE | wbc_to_write_flags(wbc),
GFP_NOFS, &iomap_ioend_bioset);
bio->bi_iter.bi_sector = sector;
wbc_init_bio(wbc, bio);
ioend = container_of(bio, struct iomap_ioend, io_inline_bio);
INIT_LIST_HEAD(&ioend->io_list);
ioend->io_type = wpc->iomap.type;
ioend->io_flags = wpc->iomap.flags;
ioend->io_inode = inode;
ioend->io_size = 0;
ioend->io_folios = 0;
ioend->io_offset = offset;
ioend->io_bio = bio;
ioend->io_sector = sector;
return ioend;
}
/*
* Allocate a new bio, and chain the old bio to the new one.
*
* Note that we have to perform the chaining in this unintuitive order
* so that the bi_private linkage is set up in the right direction for the
* traversal in iomap_finish_ioend().
*/
static struct bio *
iomap_chain_bio(struct bio *prev)
{
struct bio *new;
new = bio_alloc(prev->bi_bdev, BIO_MAX_VECS, prev->bi_opf, GFP_NOFS);
bio_clone_blkg_association(new, prev);
new->bi_iter.bi_sector = bio_end_sector(prev);
bio_chain(prev, new);
bio_get(prev); /* for iomap_finish_ioend */
submit_bio(prev);
return new;
}
static bool
iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t offset,
sector_t sector)
{
if ((wpc->iomap.flags & IOMAP_F_SHARED) !=
(wpc->ioend->io_flags & IOMAP_F_SHARED))
return false;
if (wpc->iomap.type != wpc->ioend->io_type)
return false;
if (offset != wpc->ioend->io_offset + wpc->ioend->io_size)
return false;
if (sector != bio_end_sector(wpc->ioend->io_bio))
return false;
/*
* Limit ioend bio chain lengths to minimise IO completion latency. This
* also prevents long tight loops ending page writeback on all the
* folios in the ioend.
*/
if (wpc->ioend->io_folios >= IOEND_BATCH_SIZE)
return false;
return true;
}
/*
* Test to see if we have an existing ioend structure that we could append to
* first; otherwise finish off the current ioend and start another.
*/
static void
iomap_add_to_ioend(struct inode *inode, loff_t pos, struct folio *folio,
struct iomap_page *iop, struct iomap_writepage_ctx *wpc,
struct writeback_control *wbc, struct list_head *iolist)
{
sector_t sector = iomap_sector(&wpc->iomap, pos);
unsigned len = i_blocksize(inode);
size_t poff = offset_in_folio(folio, pos);
if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos, sector)) {
if (wpc->ioend)
list_add(&wpc->ioend->io_list, iolist);
wpc->ioend = iomap_alloc_ioend(inode, wpc, pos, sector, wbc);
}
if (!bio_add_folio(wpc->ioend->io_bio, folio, len, poff)) {
wpc->ioend->io_bio = iomap_chain_bio(wpc->ioend->io_bio);
bio_add_folio(wpc->ioend->io_bio, folio, len, poff);
}
if (iop)
atomic_add(len, &iop->write_bytes_pending);
wpc->ioend->io_size += len;
wbc_account_cgroup_owner(wbc, &folio->page, len);
}
/*
* We implement an immediate ioend submission policy here to avoid needing to
* chain multiple ioends and hence nest mempool allocations which can violate
* the forward progress guarantees we need to provide. The current ioend we're
* adding blocks to is cached in the writepage context, and if the new block
* doesn't append to the cached ioend, it will create a new ioend and cache that
* instead.
*
* If a new ioend is created and cached, the old ioend is returned and queued
* locally for submission once the entire page is processed or an error has been
* detected. While ioends are submitted immediately after they are completed,
* batching optimisations are provided by higher level block plugging.
*
* At the end of a writeback pass, there will be a cached ioend remaining on the
* writepage context that the caller will need to submit.
*/
static int
iomap_writepage_map(struct iomap_writepage_ctx *wpc,
struct writeback_control *wbc, struct inode *inode,
struct folio *folio, u64 end_pos)
{
struct iomap_page *iop = iomap_page_create(inode, folio);
struct iomap_ioend *ioend, *next;
unsigned len = i_blocksize(inode);
unsigned nblocks = i_blocks_per_folio(inode, folio);
u64 pos = folio_pos(folio);
int error = 0, count = 0, i;
LIST_HEAD(submit_list);
WARN_ON_ONCE(iop && atomic_read(&iop->write_bytes_pending) != 0);
/*
* Walk through the folio to find areas to write back. If we
* run off the end of the current map or find the current map
* invalid, grab a new one.
*/
for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
if (iop && !test_bit(i, iop->uptodate))
continue;
error = wpc->ops->map_blocks(wpc, inode, pos);
if (error)
break;
if (WARN_ON_ONCE(wpc->iomap.type == IOMAP_INLINE))
continue;
if (wpc->iomap.type == IOMAP_HOLE)
continue;
iomap_add_to_ioend(inode, pos, folio, iop, wpc, wbc,
&submit_list);
count++;
}
if (count)
wpc->ioend->io_folios++;
WARN_ON_ONCE(!wpc->ioend && !list_empty(&submit_list));
WARN_ON_ONCE(!folio_test_locked(folio));
WARN_ON_ONCE(folio_test_writeback(folio));
WARN_ON_ONCE(folio_test_dirty(folio));
/*
* We cannot cancel the ioend directly here on error. We may have
* already set other pages under writeback and hence we have to run I/O
* completion to mark the error state of the pages under writeback
* appropriately.
*/
if (unlikely(error)) {
/*
* Let the filesystem know what portion of the current page
* failed to map. If the page hasn't been added to ioend, it
* won't be affected by I/O completion and we must unlock it
* now.
*/
if (wpc->ops->discard_folio)
wpc->ops->discard_folio(folio, pos);
if (!count) {
folio_clear_uptodate(folio);
folio_unlock(folio);
goto done;
}
}
folio_start_writeback(folio);
folio_unlock(folio);
/*
* Preserve the original error if there was one; catch
* submission errors here and propagate into subsequent ioend
* submissions.
*/
list_for_each_entry_safe(ioend, next, &submit_list, io_list) {
int error2;
list_del_init(&ioend->io_list);
error2 = iomap_submit_ioend(wpc, ioend, error);
if (error2 && !error)
error = error2;
}
/*
* We can end up here with no error and nothing to write only if we race
* with a partial page truncate on a sub-page block sized filesystem.
*/
if (!count)
folio_end_writeback(folio);
done:
mapping_set_error(folio->mapping, error);
return error;
}
/*
* Write out a dirty page.
*
* For delalloc space on the page, we need to allocate space and flush it.
* For unwritten space on the page, we need to start the conversion to
* regular allocated space.
*/
static int
iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
{
struct folio *folio = page_folio(page);
struct iomap_writepage_ctx *wpc = data;
struct inode *inode = folio->mapping->host;
u64 end_pos, isize;
trace_iomap_writepage(inode, folio_pos(folio), folio_size(folio));
/*
* Refuse to write the folio out if we're called from reclaim context.
*
* This avoids stack overflows when called from deeply used stacks in
* random callers for direct reclaim or memcg reclaim. We explicitly
* allow reclaim from kswapd as the stack usage there is relatively low.
*
* This should never happen except in the case of a VM regression so
* warn about it.
*/
if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
PF_MEMALLOC))
goto redirty;
/*
* Is this folio beyond the end of the file?
*
* The folio index is less than the end_index, adjust the end_pos
* to the highest offset that this folio should represent.
* -----------------------------------------------------
* | file mapping | <EOF> |
* -----------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | |
* ^--------------------------------^----------|--------
* | desired writeback range | see else |
* ---------------------------------^------------------|
*/
isize = i_size_read(inode);
end_pos = folio_pos(folio) + folio_size(folio);
if (end_pos > isize) {
/*
* Check whether the page to write out is beyond or straddles
* i_size or not.
* -------------------------------------------------------
* | file mapping | <EOF> |
* -------------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | Beyond |
* ^--------------------------------^-----------|---------
* | | Straddles |
* ---------------------------------^-----------|--------|
*/
size_t poff = offset_in_folio(folio, isize);
pgoff_t end_index = isize >> PAGE_SHIFT;
/*
* Skip the page if it's fully outside i_size, e.g. due to a
* truncate operation that's in progress. We must redirty the
* page so that reclaim stops reclaiming it. Otherwise
* iomap_vm_releasepage() is called on it and gets confused.
*
* Note that the end_index is unsigned long. If the given
* offset is greater than 16TB on a 32-bit system then if we
* checked if the page is fully outside i_size with
* "if (page->index >= end_index + 1)", "end_index + 1" would
* overflow and evaluate to 0. Hence this page would be
* redirtied and written out repeatedly, which would result in
* an infinite loop; the user program performing this operation
* would hang. Instead, we can detect this situation by
* checking if the page is totally beyond i_size or if its
* offset is just equal to the EOF.
*/
if (folio->index > end_index ||
(folio->index == end_index && poff == 0))
goto redirty;
/*
* The page straddles i_size. It must be zeroed out on each
* and every writepage invocation because it may be mmapped.
* "A file is mapped in multiples of the page size. For a file
* that is not a multiple of the page size, the remaining
* memory is zeroed when mapped, and writes to that region are
* not written out to the file."
*/
folio_zero_segment(folio, poff, folio_size(folio));
end_pos = isize;
}
return iomap_writepage_map(wpc, wbc, inode, folio, end_pos);
redirty:
folio_redirty_for_writepage(wbc, folio);
folio_unlock(folio);
return 0;
}
int
iomap_writepage(struct page *page, struct writeback_control *wbc,
struct iomap_writepage_ctx *wpc,
const struct iomap_writeback_ops *ops)
{
int ret;
wpc->ops = ops;
ret = iomap_do_writepage(page, wbc, wpc);
if (!wpc->ioend)
return ret;
return iomap_submit_ioend(wpc, wpc->ioend, ret);
}
EXPORT_SYMBOL_GPL(iomap_writepage);
int
iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
struct iomap_writepage_ctx *wpc,
const struct iomap_writeback_ops *ops)
{
int ret;
wpc->ops = ops;
ret = write_cache_pages(mapping, wbc, iomap_do_writepage, wpc);
if (!wpc->ioend)
return ret;
return iomap_submit_ioend(wpc, wpc->ioend, ret);
}
EXPORT_SYMBOL_GPL(iomap_writepages);
static int __init iomap_init(void)
{
return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
offsetof(struct iomap_ioend, io_inline_bio),
BIOSET_NEED_BVECS);
}
fs_initcall(iomap_init);
