// SPDX-License-Identifier: GPL-2.0 /* * Copyright (C) 2010 Red Hat, Inc. * Copyright (C) 2016-2019 Christoph Hellwig. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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, unsigned int flags) { struct iomap_page *iop = to_iomap_page(folio); unsigned int nr_blocks = i_blocks_per_folio(inode, folio); gfp_t gfp; if (iop || nr_blocks <= 1) return iop; if (flags & IOMAP_NOWAIT) gfp = GFP_NOWAIT; else gfp = GFP_NOFS | __GFP_NOFAIL; iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)), gfp); if (iop) { 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 (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, iter->flags); 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, 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, 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_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(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_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); bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags) { trace_iomap_release_folio(folio->mapping->host, folio_pos(folio), folio_size(folio)); /* * mm accommodates an old ext3 case where clean folios might * not have had the dirty bit cleared. Thus, it can send actual * dirty folios to ->release_folio() via shrink_active_list(); * skip those here. */ if (folio_test_dirty(folio) || folio_test_writeback(folio)) return false; iomap_page_release(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); 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); 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(&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; 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 (folio_test_uptodate(folio)) return 0; folio_clear_error(folio); iop = iomap_page_create(iter->inode, folio, iter->flags); if ((iter->flags & IOMAP_NOWAIT) && !iop && nr_blocks > 1) return -EAGAIN; 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, 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; if (iter->flags & IOMAP_NOWAIT) fgp |= FGP_NOWAIT; 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 = (iter->flags & IOMAP_NOWAIT) ? -EAGAIN : -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 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, 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 + 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); 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; 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: 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; page = folio_file_page(folio, pos >> PAGE_SHIFT); if (mapping_writably_mapped(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; } 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, }; int 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 (iter.pos == iocb->ki_pos) return ret; return iter.pos - iocb->ki_pos; } EXPORT_SYMBOL_GPL(iomap_file_buffered_write); /* * Scan the data range passed to us for dirty page cache folios. If we find a * dirty folio, punch out the preceeding 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, int (*punch)(struct inode *inode, loff_t offset, loff_t length)) { while (start_byte < end_byte) { struct folio *folio; /* grab locked page */ folio = filemap_lock_folio(inode->i_mapping, start_byte >> PAGE_SHIFT); if (!folio) { start_byte = ALIGN_DOWN(start_byte, PAGE_SIZE) + PAGE_SIZE; continue; } /* if dirty, punch up to offset */ if (folio_test_dirty(folio)) { if (start_byte > *punch_start_byte) { int error; error = punch(inode, *punch_start_byte, start_byte - *punch_start_byte); if (error) { folio_unlock(folio); folio_put(folio); return error; } } /* * 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_next_index(folio) << PAGE_SHIFT); } /* 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, int (*punch)(struct inode *inode, loff_t pos, loff_t length)) { 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, int (*punch)(struct inode *inode, loff_t pos, loff_t length)) { loff_t start_byte; loff_t end_byte; 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); 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; } 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 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, 0); 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; 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, 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_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(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 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 | | * ----------------------------------------------------- * | 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 | | * ------------------------------------------------------- * | 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);