/* * linux/mm/filemap.h * * Copyright (C) 1994-1999 Linus Torvalds */ #ifndef __FILEMAP_H #define __FILEMAP_H #include <linux/types.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/uio.h> #include <linux/uaccess.h> size_t __filemap_copy_from_user_iovec_inatomic(char *vaddr, const struct iovec *iov, size_t base, size_t bytes); /* * Copy as much as we can into the page and return the number of bytes which * were sucessfully copied. If a fault is encountered then clear the page * out to (offset+bytes) and return the number of bytes which were copied. * * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache * to *NOT* zero any tail of the buffer that it failed to copy. If it does, * and if the following non-atomic copy succeeds, then there is a small window * where the target page contains neither the data before the write, nor the * data after the write (it contains zero). A read at this time will see * data that is inconsistent with any ordering of the read and the write. * (This has been detected in practice). */ static inline size_t filemap_copy_from_user(struct page *page, unsigned long offset, const char __user *buf, unsigned bytes) { char *kaddr; int left; kaddr = kmap_atomic(page, KM_USER0); left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes); kunmap_atomic(kaddr, KM_USER0); if (left != 0) { /* Do it the slow way */ kaddr = kmap(page); left = __copy_from_user_nocache(kaddr + offset, buf, bytes); kunmap(page); } return bytes - left; } /* * This has the same sideeffects and return value as filemap_copy_from_user(). * The difference is that on a fault we need to memset the remainder of the * page (out to offset+bytes), to emulate filemap_copy_from_user()'s * single-segment behaviour. */ static inline size_t filemap_copy_from_user_iovec(struct page *page, unsigned long offset, const struct iovec *iov, size_t base, size_t bytes) { char *kaddr; size_t copied; kaddr = kmap_atomic(page, KM_USER0); copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov, base, bytes); kunmap_atomic(kaddr, KM_USER0); if (copied != bytes) { kaddr = kmap(page); copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov, base, bytes); if (bytes - copied) memset(kaddr + offset + copied, 0, bytes - copied); kunmap(page); } return copied; } static inline void filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) { const struct iovec *iov = *iovp; size_t base = *basep; do { int copy = min(bytes, iov->iov_len - base); bytes -= copy; base += copy; if (iov->iov_len == base) { iov++; base = 0; } } while (bytes); *iovp = iov; *basep = base; } #endif