// SPDX-License-Identifier: GPL-2.0 /* * Copyright (C) 2017 Red Hat, Inc. * Copyright (c) 2018 Christoph Hellwig. */ #include <linux/module.h> #include <linux/compiler.h> #include <linux/fs.h> #include <linux/iomap.h> #include <linux/pagemap.h> #include <linux/pagevec.h> /* * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff. * Returns true if found and updates @lastoff to the offset in file. */ static bool page_seek_hole_data(struct inode *inode, struct page *page, loff_t *lastoff, int whence) { const struct address_space_operations *ops = inode->i_mapping->a_ops; unsigned int bsize = i_blocksize(inode), off; bool seek_data = whence == SEEK_DATA; loff_t poff = page_offset(page); if (WARN_ON_ONCE(*lastoff >= poff + PAGE_SIZE)) return false; if (*lastoff < poff) { /* * Last offset smaller than the start of the page means we found * a hole: */ if (whence == SEEK_HOLE) return true; *lastoff = poff; } /* * Just check the page unless we can and should check block ranges: */ if (bsize == PAGE_SIZE || !ops->is_partially_uptodate) return PageUptodate(page) == seek_data; lock_page(page); if (unlikely(page->mapping != inode->i_mapping)) goto out_unlock_not_found; for (off = 0; off < PAGE_SIZE; off += bsize) { if (offset_in_page(*lastoff) >= off + bsize) continue; if (ops->is_partially_uptodate(page, off, bsize) == seek_data) { unlock_page(page); return true; } *lastoff = poff + off + bsize; } out_unlock_not_found: unlock_page(page); return false; } /* * Seek for SEEK_DATA / SEEK_HOLE in the page cache. * * Within unwritten extents, the page cache determines which parts are holes * and which are data: uptodate buffer heads count as data; everything else * counts as a hole. * * Returns the resulting offset on successs, and -ENOENT otherwise. */ static loff_t page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length, int whence) { pgoff_t index = offset >> PAGE_SHIFT; pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE); loff_t lastoff = offset; struct pagevec pvec; if (length <= 0) return -ENOENT; pagevec_init(&pvec); do { unsigned nr_pages, i; nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index, end - 1); if (nr_pages == 0) break; for (i = 0; i < nr_pages; i++) { struct page *page = pvec.pages[i]; if (page_seek_hole_data(inode, page, &lastoff, whence)) goto check_range; lastoff = page_offset(page) + PAGE_SIZE; } pagevec_release(&pvec); } while (index < end); /* When no page at lastoff and we are not done, we found a hole. */ if (whence != SEEK_HOLE) goto not_found; check_range: if (lastoff < offset + length) goto out; not_found: lastoff = -ENOENT; out: pagevec_release(&pvec); return lastoff; } static loff_t iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length, void *data, struct iomap *iomap) { switch (iomap->type) { case IOMAP_UNWRITTEN: offset = page_cache_seek_hole_data(inode, offset, length, SEEK_HOLE); if (offset < 0) return length; /* fall through */ case IOMAP_HOLE: *(loff_t *)data = offset; return 0; default: return length; } } loff_t iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops) { loff_t size = i_size_read(inode); loff_t length = size - offset; loff_t ret; /* Nothing to be found before or beyond the end of the file. */ if (offset < 0 || offset >= size) return -ENXIO; while (length > 0) { ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, &offset, iomap_seek_hole_actor); if (ret < 0) return ret; if (ret == 0) break; offset += ret; length -= ret; } return offset; } EXPORT_SYMBOL_GPL(iomap_seek_hole); static loff_t iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length, void *data, struct iomap *iomap) { switch (iomap->type) { case IOMAP_HOLE: return length; case IOMAP_UNWRITTEN: offset = page_cache_seek_hole_data(inode, offset, length, SEEK_DATA); if (offset < 0) return length; /*FALLTHRU*/ default: *(loff_t *)data = offset; return 0; } } loff_t iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops) { loff_t size = i_size_read(inode); loff_t length = size - offset; loff_t ret; /* Nothing to be found before or beyond the end of the file. */ if (offset < 0 || offset >= size) return -ENXIO; while (length > 0) { ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, &offset, iomap_seek_data_actor); if (ret < 0) return ret; if (ret == 0) break; offset += ret; length -= ret; } if (length <= 0) return -ENXIO; return offset; } EXPORT_SYMBOL_GPL(iomap_seek_data);