diff options
Diffstat (limited to 'fs/iomap/buffered-io.c')
| -rw-r--r-- | fs/iomap/buffered-io.c | 2002 |
1 files changed, 2002 insertions, 0 deletions
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c new file mode 100644 index 0000000000..2bc0aa23fd --- /dev/null +++ b/fs/iomap/buffered-io.c @@ -0,0 +1,2002 @@ +// 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 + +typedef int (*iomap_punch_t)(struct inode *inode, loff_t offset, loff_t length); +/* + * Structure allocated for each folio to track per-block uptodate, dirty state + * and I/O completions. + */ +struct iomap_folio_state { + atomic_t read_bytes_pending; + atomic_t write_bytes_pending; + spinlock_t state_lock; + + /* + * Each block has two bits in this bitmap: + * Bits [0..blocks_per_folio) has the uptodate status. + * Bits [b_p_f...(2*b_p_f)) has the dirty status. + */ + unsigned long state[]; +}; + +static struct bio_set iomap_ioend_bioset; + +static inline bool ifs_is_fully_uptodate(struct folio *folio, + struct iomap_folio_state *ifs) +{ + struct inode *inode = folio->mapping->host; + + return bitmap_full(ifs->state, i_blocks_per_folio(inode, folio)); +} + +static inline bool ifs_block_is_uptodate(struct iomap_folio_state *ifs, + unsigned int block) +{ + return test_bit(block, ifs->state); +} + +static void ifs_set_range_uptodate(struct folio *folio, + struct iomap_folio_state *ifs, size_t off, size_t len) +{ + struct inode *inode = folio->mapping->host; + unsigned int first_blk = off >> inode->i_blkbits; + unsigned int last_blk = (off + len - 1) >> inode->i_blkbits; + unsigned int nr_blks = last_blk - first_blk + 1; + unsigned long flags; + + spin_lock_irqsave(&ifs->state_lock, flags); + bitmap_set(ifs->state, first_blk, nr_blks); + if (ifs_is_fully_uptodate(folio, ifs)) + folio_mark_uptodate(folio); + spin_unlock_irqrestore(&ifs->state_lock, flags); +} + +static void iomap_set_range_uptodate(struct folio *folio, size_t off, + size_t len) +{ + struct iomap_folio_state *ifs = folio->private; + + if (ifs) + ifs_set_range_uptodate(folio, ifs, off, len); + else + folio_mark_uptodate(folio); +} + +static inline bool ifs_block_is_dirty(struct folio *folio, + struct iomap_folio_state *ifs, int block) +{ + struct inode *inode = folio->mapping->host; + unsigned int blks_per_folio = i_blocks_per_folio(inode, folio); + + return test_bit(block + blks_per_folio, ifs->state); +} + +static void ifs_clear_range_dirty(struct folio *folio, + struct iomap_folio_state *ifs, size_t off, size_t len) +{ + struct inode *inode = folio->mapping->host; + unsigned int blks_per_folio = i_blocks_per_folio(inode, folio); + unsigned int first_blk = (off >> inode->i_blkbits); + unsigned int last_blk = (off + len - 1) >> inode->i_blkbits; + unsigned int nr_blks = last_blk - first_blk + 1; + unsigned long flags; + + spin_lock_irqsave(&ifs->state_lock, flags); + bitmap_clear(ifs->state, first_blk + blks_per_folio, nr_blks); + spin_unlock_irqrestore(&ifs->state_lock, flags); +} + +static void iomap_clear_range_dirty(struct folio *folio, size_t off, size_t len) +{ + struct iomap_folio_state *ifs = folio->private; + + if (ifs) + ifs_clear_range_dirty(folio, ifs, off, len); +} + +static void ifs_set_range_dirty(struct folio *folio, + struct iomap_folio_state *ifs, size_t off, size_t len) +{ + struct inode *inode = folio->mapping->host; + unsigned int blks_per_folio = i_blocks_per_folio(inode, folio); + unsigned int first_blk = (off >> inode->i_blkbits); + unsigned int last_blk = (off + len - 1) >> inode->i_blkbits; + unsigned int nr_blks = last_blk - first_blk + 1; + unsigned long flags; + + spin_lock_irqsave(&ifs->state_lock, flags); + bitmap_set(ifs->state, first_blk + blks_per_folio, nr_blks); + spin_unlock_irqrestore(&ifs->state_lock, flags); +} + +static void iomap_set_range_dirty(struct folio *folio, size_t off, size_t len) +{ + struct iomap_folio_state *ifs = folio->private; + + if (ifs) + ifs_set_range_dirty(folio, ifs, off, len); +} + +static struct iomap_folio_state *ifs_alloc(struct inode *inode, + struct folio *folio, unsigned int flags) +{ + struct iomap_folio_state *ifs = folio->private; + unsigned int nr_blocks = i_blocks_per_folio(inode, folio); + gfp_t gfp; + + if (ifs || nr_blocks <= 1) + return ifs; + + if (flags & IOMAP_NOWAIT) + gfp = GFP_NOWAIT; + else + gfp = GFP_NOFS | __GFP_NOFAIL; + + /* + * ifs->state tracks two sets of state flags when the + * filesystem block size is smaller than the folio size. + * The first state tracks per-block uptodate and the + * second tracks per-block dirty state. + */ + ifs = kzalloc(struct_size(ifs, state, + BITS_TO_LONGS(2 * nr_blocks)), gfp); + if (!ifs) + return ifs; + + spin_lock_init(&ifs->state_lock); + if (folio_test_uptodate(folio)) + bitmap_set(ifs->state, 0, nr_blocks); + if (folio_test_dirty(folio)) + bitmap_set(ifs->state, nr_blocks, nr_blocks); + folio_attach_private(folio, ifs); + + return ifs; +} + +static void ifs_free(struct folio *folio) +{ + struct iomap_folio_state *ifs = folio_detach_private(folio); + + if (!ifs) + return; + WARN_ON_ONCE(atomic_read(&ifs->read_bytes_pending)); + WARN_ON_ONCE(atomic_read(&ifs->write_bytes_pending)); + WARN_ON_ONCE(ifs_is_fully_uptodate(folio, ifs) != + folio_test_uptodate(folio)); + kfree(ifs); +} + +/* + * 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_folio_state *ifs = folio->private; + 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 (ifs) { + unsigned int i; + + /* move forward for each leading block marked uptodate */ + for (i = first; i <= last; i++) { + if (!ifs_block_is_uptodate(ifs, i)) + 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 (ifs_block_is_uptodate(ifs, i)) { + 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_finish_folio_read(struct folio *folio, size_t offset, + size_t len, int error) +{ + struct iomap_folio_state *ifs = folio->private; + + if (unlikely(error)) { + folio_clear_uptodate(folio); + folio_set_error(folio); + } else { + iomap_set_range_uptodate(folio, offset, len); + } + + if (!ifs || atomic_sub_and_test(len, &ifs->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) +{ + 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) + ifs_alloc(iter->inode, folio, iter->flags); + + 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, 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_folio_state *ifs; + 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 */ + ifs = ifs_alloc(iter->inode, folio, iter->flags); + 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, poff, plen); + goto done; + } + + ctx->cur_folio_in_bio = true; + if (ifs) + atomic_add(plen, &ifs->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_read_folio 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_nofail(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_read_folio(struct folio *folio, const struct iomap_ops *ops) +{ + 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_folio, we always + * return 0 and just set the folio error flag on errors. This + * should be cleaned up throughout the stack eventually. + */ + return 0; +} +EXPORT_SYMBOL_GPL(iomap_read_folio); + +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_folio_state *ifs = folio->private; + struct inode *inode = folio->mapping->host; + unsigned first, last, i; + + if (!ifs) + 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 (!ifs_block_is_uptodate(ifs, i)) + return false; + return true; +} +EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate); + +/** + * iomap_get_folio - get a folio reference for writing + * @iter: iteration structure + * @pos: start offset of write + * @len: Suggested size of folio to create. + * + * Returns a locked reference to the folio at @pos, or an error pointer if the + * folio could not be obtained. + */ +struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len) +{ + fgf_t fgp = FGP_WRITEBEGIN | FGP_NOFS; + + if (iter->flags & IOMAP_NOWAIT) + fgp |= FGP_NOWAIT; + fgp |= fgf_set_order(len); + + return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT, + fgp, mapping_gfp_mask(iter->inode->i_mapping)); +} +EXPORT_SYMBOL_GPL(iomap_get_folio); + +bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags) +{ + trace_iomap_release_folio(folio->mapping->host, folio_pos(folio), + folio_size(folio)); + + /* + * If the folio is dirty, we refuse to release our metadata because + * it may be partially dirty. Once we track per-block dirty state, + * we can release the metadata if every block is dirty. + */ + if (folio_test_dirty(folio)) + return false; + ifs_free(folio); + return true; +} +EXPORT_SYMBOL_GPL(iomap_release_folio); + +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); + ifs_free(folio); + } +} +EXPORT_SYMBOL_GPL(iomap_invalidate_folio); + +bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio) +{ + struct inode *inode = mapping->host; + size_t len = folio_size(folio); + + ifs_alloc(inode, folio, 0); + iomap_set_range_dirty(folio, 0, len); + return filemap_dirty_folio(mapping, folio); +} +EXPORT_SYMBOL_GPL(iomap_dirty_folio); + +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 - 1); +} + +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_nofail(&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_folio_state *ifs; + 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); + unsigned int nr_blocks = i_blocks_per_folio(iter->inode, folio); + size_t from = offset_in_folio(folio, pos), to = from + len; + size_t poff, plen; + + /* + * If the write or zeroing completely overlaps the current folio, then + * entire folio will be dirtied so there is no need for + * per-block state tracking structures to be attached to this folio. + * For the unshare case, we must read in the ondisk contents because we + * are not changing pagecache contents. + */ + if (!(iter->flags & IOMAP_UNSHARE) && pos <= folio_pos(folio) && + pos + len >= folio_pos(folio) + folio_size(folio)) + return 0; + + ifs = ifs_alloc(iter->inode, folio, iter->flags); + if ((iter->flags & IOMAP_NOWAIT) && !ifs && nr_blocks > 1) + return -EAGAIN; + + 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; + + if (iter->flags & IOMAP_NOWAIT) + return -EAGAIN; + + status = iomap_read_folio_sync(block_start, folio, + poff, plen, srcmap); + if (status) + return status; + } + iomap_set_range_uptodate(folio, poff, plen); + } while ((block_start += plen) < block_end); + + return 0; +} + +static struct folio *__iomap_get_folio(struct iomap_iter *iter, loff_t pos, + size_t len) +{ + const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops; + + if (folio_ops && folio_ops->get_folio) + return folio_ops->get_folio(iter, pos, len); + else + return iomap_get_folio(iter, pos, len); +} + +static void __iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret, + struct folio *folio) +{ + const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops; + + if (folio_ops && folio_ops->put_folio) { + folio_ops->put_folio(iter->inode, pos, ret, folio); + } else { + folio_unlock(folio); + folio_put(folio); + } +} + +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(struct iomap_iter *iter, loff_t pos, + size_t len, struct folio **foliop) +{ + const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops; + const struct iomap *srcmap = iomap_iter_srcmap(iter); + struct folio *folio; + 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)); + + folio = __iomap_get_folio(iter, pos, len); + if (IS_ERR(folio)) + return PTR_ERR(folio); + + /* + * Now we have a locked folio, before we do anything with it we need to + * check that the iomap we have cached is not stale. The inode extent + * mapping can change due to concurrent IO in flight (e.g. + * IOMAP_UNWRITTEN state can change and memory reclaim could have + * reclaimed a previously partially written page at this index after IO + * completion before this write reaches this file offset) and hence we + * could do the wrong thing here (zero a page range incorrectly or fail + * to zero) and corrupt data. + */ + if (folio_ops && folio_ops->iomap_valid) { + bool iomap_valid = folio_ops->iomap_valid(iter->inode, + &iter->iomap); + if (!iomap_valid) { + iter->iomap.flags |= IOMAP_F_STALE; + status = 0; + goto out_unlock; + } + } + + 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: + __iomap_put_folio(iter, pos, 0, folio); + iomap_write_failed(iter->inode, pos, len); + + return status; +} + +static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len, + size_t copied, struct folio *folio) +{ + flush_dcache_folio(folio); + + /* + * The blocks that were entirely written will now be uptodate, so we + * don't have to worry about a read_folio 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 + * read_folio 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, offset_in_folio(folio, pos), len); + iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied); + 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 *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; + } + __iomap_put_folio(iter, pos, ret, folio); + + if (old_size < pos) + pagecache_isize_extended(iter->inode, old_size, pos); + if (ret < len) + iomap_write_failed(iter->inode, pos + ret, len - ret); + return ret; +} + +static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) +{ + loff_t length = iomap_length(iter); + size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER; + loff_t pos = iter->pos; + ssize_t written = 0; + long status = 0; + struct address_space *mapping = iter->inode->i_mapping; + unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0; + + do { + struct folio *folio; + size_t offset; /* Offset into folio */ + size_t bytes; /* Bytes to write to folio */ + size_t copied; /* Bytes copied from user */ + + bytes = iov_iter_count(i); +retry: + offset = pos & (chunk - 1); + bytes = min(chunk - offset, bytes); + status = balance_dirty_pages_ratelimited_flags(mapping, + bdp_flags); + if (unlikely(status)) + break; + + 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. + * + * For async buffered writes the assumption is that the user + * page has already been faulted in. This can be optimized by + * faulting the user page. + */ + 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; + if (iter->iomap.flags & IOMAP_F_STALE) + break; + + offset = offset_in_folio(folio, pos); + if (bytes > folio_size(folio) - offset) + bytes = folio_size(folio) - offset; + + if (mapping_writably_mapped(mapping)) + flush_dcache_folio(folio); + + copied = copy_folio_from_iter_atomic(folio, 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 (chunk > PAGE_SIZE) + chunk /= 2; + if (copied) { + bytes = copied; + goto retry; + } + } else { + pos += status; + written += status; + length -= status; + } + } while (iov_iter_count(i) && length); + + if (status == -EAGAIN) { + iov_iter_revert(i, written); + return -EAGAIN; + } + 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, + }; + ssize_t ret; + + if (iocb->ki_flags & IOCB_NOWAIT) + iter.flags |= IOMAP_NOWAIT; + + while ((ret = iomap_iter(&iter, ops)) > 0) + iter.processed = iomap_write_iter(&iter, i); + + if (unlikely(iter.pos == iocb->ki_pos)) + return ret; + ret = iter.pos - iocb->ki_pos; + iocb->ki_pos = iter.pos; + return ret; +} +EXPORT_SYMBOL_GPL(iomap_file_buffered_write); + +static int iomap_write_delalloc_ifs_punch(struct inode *inode, + struct folio *folio, loff_t start_byte, loff_t end_byte, + iomap_punch_t punch) +{ + unsigned int first_blk, last_blk, i; + loff_t last_byte; + u8 blkbits = inode->i_blkbits; + struct iomap_folio_state *ifs; + int ret = 0; + + /* + * When we have per-block dirty tracking, there can be + * blocks within a folio which are marked uptodate + * but not dirty. In that case it is necessary to punch + * out such blocks to avoid leaking any delalloc blocks. + */ + ifs = folio->private; + if (!ifs) + return ret; + + last_byte = min_t(loff_t, end_byte - 1, + folio_pos(folio) + folio_size(folio) - 1); + first_blk = offset_in_folio(folio, start_byte) >> blkbits; + last_blk = offset_in_folio(folio, last_byte) >> blkbits; + for (i = first_blk; i <= last_blk; i++) { + if (!ifs_block_is_dirty(folio, ifs, i)) { + ret = punch(inode, folio_pos(folio) + (i << blkbits), + 1 << blkbits); + if (ret) + return ret; + } + } + + return ret; +} + + +static int iomap_write_delalloc_punch(struct inode *inode, struct folio *folio, + loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte, + iomap_punch_t punch) +{ + int ret = 0; + + if (!folio_test_dirty(folio)) + return ret; + + /* if dirty, punch up to offset */ + if (start_byte > *punch_start_byte) { + ret = punch(inode, *punch_start_byte, + start_byte - *punch_start_byte); + if (ret) + return ret; + } + + /* Punch non-dirty blocks within folio */ + ret = iomap_write_delalloc_ifs_punch(inode, folio, start_byte, + end_byte, punch); + if (ret) + return ret; + + /* + * Make sure the next punch start is correctly bound to + * the end of this data range, not the end of the folio. + */ + *punch_start_byte = min_t(loff_t, end_byte, + folio_pos(folio) + folio_size(folio)); + + return ret; +} + +/* + * Scan the data range passed to us for dirty page cache folios. If we find a + * dirty folio, punch out the preceding range and update the offset from which + * the next punch will start from. + * + * We can punch out storage reservations under clean pages because they either + * contain data that has been written back - in which case the delalloc punch + * over that range is a no-op - or they have been read faults in which case they + * contain zeroes and we can remove the delalloc backing range and any new + * writes to those pages will do the normal hole filling operation... + * + * This makes the logic simple: we only need to keep the delalloc extents only + * over the dirty ranges of the page cache. + * + * This function uses [start_byte, end_byte) intervals (i.e. open ended) to + * simplify range iterations. + */ +static int iomap_write_delalloc_scan(struct inode *inode, + loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte, + iomap_punch_t punch) +{ + while (start_byte < end_byte) { + struct folio *folio; + int ret; + + /* grab locked page */ + folio = filemap_lock_folio(inode->i_mapping, + start_byte >> PAGE_SHIFT); + if (IS_ERR(folio)) { + start_byte = ALIGN_DOWN(start_byte, PAGE_SIZE) + + PAGE_SIZE; + continue; + } + + ret = iomap_write_delalloc_punch(inode, folio, punch_start_byte, + start_byte, end_byte, punch); + if (ret) { + folio_unlock(folio); + folio_put(folio); + return ret; + } + + /* move offset to start of next folio in range */ + start_byte = folio_next_index(folio) << PAGE_SHIFT; + folio_unlock(folio); + folio_put(folio); + } + return 0; +} + +/* + * Punch out all the delalloc blocks in the range given except for those that + * have dirty data still pending in the page cache - those are going to be + * written and so must still retain the delalloc backing for writeback. + * + * As we are scanning the page cache for data, we don't need to reimplement the + * wheel - mapping_seek_hole_data() does exactly what we need to identify the + * start and end of data ranges correctly even for sub-folio block sizes. This + * byte range based iteration is especially convenient because it means we + * don't have to care about variable size folios, nor where the start or end of + * the data range lies within a folio, if they lie within the same folio or even + * if there are multiple discontiguous data ranges within the folio. + * + * It should be noted that mapping_seek_hole_data() is not aware of EOF, and so + * can return data ranges that exist in the cache beyond EOF. e.g. a page fault + * spanning EOF will initialise the post-EOF data to zeroes and mark it up to + * date. A write page fault can then mark it dirty. If we then fail a write() + * beyond EOF into that up to date cached range, we allocate a delalloc block + * beyond EOF and then have to punch it out. Because the range is up to date, + * mapping_seek_hole_data() will return it, and we will skip the punch because + * the folio is dirty. THis is incorrect - we always need to punch out delalloc + * beyond EOF in this case as writeback will never write back and covert that + * delalloc block beyond EOF. Hence we limit the cached data scan range to EOF, + * resulting in always punching out the range from the EOF to the end of the + * range the iomap spans. + * + * Intervals are of the form [start_byte, end_byte) (i.e. open ended) because it + * matches the intervals returned by mapping_seek_hole_data(). i.e. SEEK_DATA + * returns the start of a data range (start_byte), and SEEK_HOLE(start_byte) + * returns the end of the data range (data_end). Using closed intervals would + * require sprinkling this code with magic "+ 1" and "- 1" arithmetic and expose + * the code to subtle off-by-one bugs.... + */ +static int iomap_write_delalloc_release(struct inode *inode, + loff_t start_byte, loff_t end_byte, iomap_punch_t punch) +{ + loff_t punch_start_byte = start_byte; + loff_t scan_end_byte = min(i_size_read(inode), end_byte); + int error = 0; + + /* + * Lock the mapping to avoid races with page faults re-instantiating + * folios and dirtying them via ->page_mkwrite whilst we walk the + * cache and perform delalloc extent removal. Failing to do this can + * leave dirty pages with no space reservation in the cache. + */ + filemap_invalidate_lock(inode->i_mapping); + while (start_byte < scan_end_byte) { + loff_t data_end; + + start_byte = mapping_seek_hole_data(inode->i_mapping, + start_byte, scan_end_byte, SEEK_DATA); + /* + * If there is no more data to scan, all that is left is to + * punch out the remaining range. + */ + if (start_byte == -ENXIO || start_byte == scan_end_byte) + break; + if (start_byte < 0) { + error = start_byte; + goto out_unlock; + } + WARN_ON_ONCE(start_byte < punch_start_byte); + WARN_ON_ONCE(start_byte > scan_end_byte); + + /* + * We find the end of this contiguous cached data range by + * seeking from start_byte to the beginning of the next hole. + */ + data_end = mapping_seek_hole_data(inode->i_mapping, start_byte, + scan_end_byte, SEEK_HOLE); + if (data_end < 0) { + error = data_end; + goto out_unlock; + } + WARN_ON_ONCE(data_end <= start_byte); + WARN_ON_ONCE(data_end > scan_end_byte); + + error = iomap_write_delalloc_scan(inode, &punch_start_byte, + start_byte, data_end, punch); + if (error) + goto out_unlock; + + /* The next data search starts at the end of this one. */ + start_byte = data_end; + } + + if (punch_start_byte < end_byte) + error = punch(inode, punch_start_byte, + end_byte - punch_start_byte); +out_unlock: + filemap_invalidate_unlock(inode->i_mapping); + return error; +} + +/* + * When a short write occurs, the filesystem may need to remove reserved space + * that was allocated in ->iomap_begin from it's ->iomap_end method. For + * filesystems that use delayed allocation, we need to punch out delalloc + * extents from the range that are not dirty in the page cache. As the write can + * race with page faults, there can be dirty pages over the delalloc extent + * outside the range of a short write but still within the delalloc extent + * allocated for this iomap. + * + * This function uses [start_byte, end_byte) intervals (i.e. open ended) to + * simplify range iterations. + * + * The punch() callback *must* only punch delalloc extents in the range passed + * to it. It must skip over all other types of extents in the range and leave + * them completely unchanged. It must do this punch atomically with respect to + * other extent modifications. + * + * The punch() callback may be called with a folio locked to prevent writeback + * extent allocation racing at the edge of the range we are currently punching. + * The locked folio may or may not cover the range being punched, so it is not + * safe for the punch() callback to lock folios itself. + * + * Lock order is: + * + * inode->i_rwsem (shared or exclusive) + * inode->i_mapping->invalidate_lock (exclusive) + * folio_lock() + * ->punch + * internal filesystem allocation lock + */ +int iomap_file_buffered_write_punch_delalloc(struct inode *inode, + struct iomap *iomap, loff_t pos, loff_t length, + ssize_t written, iomap_punch_t punch) +{ + loff_t start_byte; + loff_t end_byte; + unsigned int blocksize = i_blocksize(inode); + + if (iomap->type != IOMAP_DELALLOC) + return 0; + + /* If we didn't reserve the blocks, we're not allowed to punch them. */ + if (!(iomap->flags & IOMAP_F_NEW)) + return 0; + + /* + * start_byte refers to the first unused block after a short write. If + * nothing was written, round offset down to point at the first block in + * the range. + */ + if (unlikely(!written)) + start_byte = round_down(pos, blocksize); + else + start_byte = round_up(pos + written, blocksize); + end_byte = round_up(pos + length, blocksize); + + /* Nothing to do if we've written the entire delalloc extent */ + if (start_byte >= end_byte) + return 0; + + return iomap_write_delalloc_release(inode, start_byte, end_byte, + punch); +} +EXPORT_SYMBOL_GPL(iomap_file_buffered_write_punch_delalloc); + +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); + 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 { + 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 (unlikely(status)) + return status; + if (iomap->flags & IOMAP_F_STALE) + break; + + offset = offset_in_folio(folio, pos); + if (bytes > folio_size(folio) - offset) + bytes = folio_size(folio) - offset; + + bytes = iomap_write_end(iter, pos, bytes, bytes, folio); + if (WARN_ON_ONCE(bytes == 0)) + return -EIO; + + cond_resched(); + + pos += bytes; + written += bytes; + length -= bytes; + + balance_dirty_pages_ratelimited(iter->inode->i_mapping); + } while (length > 0); + + 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; + if (iter->iomap.flags & IOMAP_F_STALE) + break; + + 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; + } while (length > 0); + + if (did_zero) + *did_zero = true; + 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 vmf_fs_error(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_folio_state *ifs = folio->private; + + if (error) { + folio_set_error(folio); + mapping_set_error(inode->i_mapping, error); + } + + WARN_ON_ONCE(i_blocks_per_folio(inode, folio) > 1 && !ifs); + WARN_ON_ONCE(ifs && atomic_read(&ifs->write_bytes_pending) <= 0); + + if (!ifs || atomic_sub_and_test(len, &ifs->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_folio_state *ifs, 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_nofail(wpc->ioend->io_bio, folio, len, poff); + } + + if (ifs) + atomic_add(len, &ifs->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_folio_state *ifs = folio->private; + 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(end_pos <= pos); + + if (!ifs && nblocks > 1) { + ifs = ifs_alloc(inode, folio, 0); + iomap_set_range_dirty(folio, 0, end_pos - pos); + } + + WARN_ON_ONCE(ifs && atomic_read(&ifs->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 (ifs && !ifs_block_is_dirty(folio, ifs, i)) + continue; + + error = wpc->ops->map_blocks(wpc, inode, pos); + if (error) + break; + trace_iomap_writepage_map(inode, &wpc->iomap); + if (WARN_ON_ONCE(wpc->iomap.type == IOMAP_INLINE)) + continue; + if (wpc->iomap.type == IOMAP_HOLE) + continue; + iomap_add_to_ioend(inode, pos, folio, ifs, 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_unlock(folio); + goto done; + } + } + + /* + * We can have dirty bits set past end of file in page_mkwrite path + * while mapping the last partial folio. Hence it's better to clear + * all the dirty bits in the folio here. + */ + iomap_clear_range_dirty(folio, 0, folio_size(folio)); + 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(inode->i_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 folio *folio, + struct writeback_control *wbc, void *data) +{ + 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've + * cleaned this page and truncate will finish things off for + * us. + * + * 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 unlock; + + /* + * 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); +unlock: + folio_unlock(folio); + return 0; +} + +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); |