// SPDX-License-Identifier: GPL-2.0 /* * mm/fadvise.c * * Copyright (C) 2002, Linus Torvalds * * 11Jan2003 Andrew Morton * Initial version. */ #include <linux/kernel.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/pagemap.h> #include <linux/backing-dev.h> #include <linux/pagevec.h> #include <linux/fadvise.h> #include <linux/writeback.h> #include <linux/syscalls.h> #include <linux/swap.h> #include <asm/unistd.h> /* * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could * deactivate the pages and clear PG_Referenced. */ static int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice) { struct inode *inode; struct address_space *mapping; struct backing_dev_info *bdi; loff_t endbyte; /* inclusive */ pgoff_t start_index; pgoff_t end_index; unsigned long nrpages; inode = file_inode(file); if (S_ISFIFO(inode->i_mode)) return -ESPIPE; mapping = file->f_mapping; if (!mapping || len < 0) return -EINVAL; bdi = inode_to_bdi(mapping->host); if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) { switch (advice) { case POSIX_FADV_NORMAL: case POSIX_FADV_RANDOM: case POSIX_FADV_SEQUENTIAL: case POSIX_FADV_WILLNEED: case POSIX_FADV_NOREUSE: case POSIX_FADV_DONTNEED: /* no bad return value, but ignore advice */ break; default: return -EINVAL; } return 0; } /* * Careful about overflows. Len == 0 means "as much as possible". Use * unsigned math because signed overflows are undefined and UBSan * complains. */ endbyte = (u64)offset + (u64)len; if (!len || endbyte < len) endbyte = -1; else endbyte--; /* inclusive */ switch (advice) { case POSIX_FADV_NORMAL: file->f_ra.ra_pages = bdi->ra_pages; spin_lock(&file->f_lock); file->f_mode &= ~FMODE_RANDOM; spin_unlock(&file->f_lock); break; case POSIX_FADV_RANDOM: spin_lock(&file->f_lock); file->f_mode |= FMODE_RANDOM; spin_unlock(&file->f_lock); break; case POSIX_FADV_SEQUENTIAL: file->f_ra.ra_pages = bdi->ra_pages * 2; spin_lock(&file->f_lock); file->f_mode &= ~FMODE_RANDOM; spin_unlock(&file->f_lock); break; case POSIX_FADV_WILLNEED: /* First and last PARTIAL page! */ start_index = offset >> PAGE_SHIFT; end_index = endbyte >> PAGE_SHIFT; /* Careful about overflow on the "+1" */ nrpages = end_index - start_index + 1; if (!nrpages) nrpages = ~0UL; /* * Ignore return value because fadvise() shall return * success even if filesystem can't retrieve a hint, */ force_page_cache_readahead(mapping, file, start_index, nrpages); break; case POSIX_FADV_NOREUSE: break; case POSIX_FADV_DONTNEED: if (!inode_write_congested(mapping->host)) __filemap_fdatawrite_range(mapping, offset, endbyte, WB_SYNC_NONE); /* * First and last FULL page! Partial pages are deliberately * preserved on the expectation that it is better to preserve * needed memory than to discard unneeded memory. */ start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT; end_index = (endbyte >> PAGE_SHIFT); /* * The page at end_index will be inclusively discarded according * by invalidate_mapping_pages(), so subtracting 1 from * end_index means we will skip the last page. But if endbyte * is page aligned or is at the end of file, we should not skip * that page - discarding the last page is safe enough. */ if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK && endbyte != inode->i_size - 1) { /* First page is tricky as 0 - 1 = -1, but pgoff_t * is unsigned, so the end_index >= start_index * check below would be true and we'll discard the whole * file cache which is not what was asked. */ if (end_index == 0) break; end_index--; } if (end_index >= start_index) { unsigned long count; /* * It's common to FADV_DONTNEED right after * the read or write that instantiates the * pages, in which case there will be some * sitting on the local LRU cache. Try to * avoid the expensive remote drain and the * second cache tree walk below by flushing * them out right away. */ lru_add_drain(); count = invalidate_mapping_pages(mapping, start_index, end_index); /* * If fewer pages were invalidated than expected then * it is possible that some of the pages were on * a per-cpu pagevec for a remote CPU. Drain all * pagevecs and try again. */ if (count < (end_index - start_index + 1)) { lru_add_drain_all(); invalidate_mapping_pages(mapping, start_index, end_index); } } break; default: return -EINVAL; } return 0; } int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice) { if (file->f_op->fadvise) return file->f_op->fadvise(file, offset, len, advice); return generic_fadvise(file, offset, len, advice); } EXPORT_SYMBOL(vfs_fadvise); #ifdef CONFIG_ADVISE_SYSCALLS int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) { struct fd f = fdget(fd); int ret; if (!f.file) return -EBADF; ret = vfs_fadvise(f.file, offset, len, advice); fdput(f); return ret; } SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice) { return ksys_fadvise64_64(fd, offset, len, advice); } #ifdef __ARCH_WANT_SYS_FADVISE64 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice) { return ksys_fadvise64_64(fd, offset, len, advice); } #endif #endif