diff options
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 250 |
1 files changed, 223 insertions, 27 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 67a03a0a9aee..ec25ba1aef5f 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1742,11 +1742,20 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes) i->count -= bytes; } -int iov_iter_fault_in_readable(struct iov_iter *i) +/* + * Fault in the first iovec of the given iov_iter, to a maximum length + * of bytes. Returns 0 on success, or non-zero if the memory could not be + * accessed (ie. because it is an invalid address). + * + * writev-intensive code may want this to prefault several iovecs -- that + * would be possible (callers must not rely on the fact that _only_ the + * first iovec will be faulted with the current implementation). + */ +int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) { - size_t seglen = min(i->iov->iov_len - i->iov_offset, i->count); char __user *buf = i->iov->iov_base + i->iov_offset; - return fault_in_pages_readable(buf, seglen); + bytes = min(bytes, i->iov->iov_len - i->iov_offset); + return fault_in_pages_readable(buf, bytes); } /* @@ -1843,6 +1852,95 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i } EXPORT_SYMBOL(generic_write_checks); +int pagecache_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + if (aops->write_begin) { + return aops->write_begin(file, mapping, pos, len, flags, + pagep, fsdata); + } else { + int ret; + pgoff_t index = pos >> PAGE_CACHE_SHIFT; + unsigned offset = pos & (PAGE_CACHE_SIZE - 1); + struct inode *inode = mapping->host; + struct page *page; +again: + page = __grab_cache_page(mapping, index); + *pagep = page; + if (!page) + return -ENOMEM; + + if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) { + /* + * There is no way to resolve a short write situation + * for a !Uptodate page (except by double copying in + * the caller done by generic_perform_write_2copy). + * + * Instead, we have to bring it uptodate here. + */ + ret = aops->readpage(file, page); + page_cache_release(page); + if (ret) { + if (ret == AOP_TRUNCATED_PAGE) + goto again; + return ret; + } + goto again; + } + + ret = aops->prepare_write(file, page, offset, offset+len); + if (ret) { + if (ret != AOP_TRUNCATED_PAGE) + unlock_page(page); + page_cache_release(page); + if (pos + len > inode->i_size) + vmtruncate(inode, inode->i_size); + if (ret == AOP_TRUNCATED_PAGE) + goto again; + } + return ret; + } +} +EXPORT_SYMBOL(pagecache_write_begin); + +int pagecache_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + int ret; + + if (aops->write_end) { + mark_page_accessed(page); + ret = aops->write_end(file, mapping, pos, len, copied, + page, fsdata); + } else { + unsigned offset = pos & (PAGE_CACHE_SIZE - 1); + struct inode *inode = mapping->host; + + flush_dcache_page(page); + ret = aops->commit_write(file, page, offset, offset+len); + unlock_page(page); + mark_page_accessed(page); + page_cache_release(page); + BUG_ON(ret == AOP_TRUNCATED_PAGE); /* can't deal with */ + + if (ret < 0) { + if (pos + len > inode->i_size) + vmtruncate(inode, inode->i_size); + } else if (ret > 0) + ret = min_t(size_t, copied, ret); + else + ret = copied; + } + + return ret; +} +EXPORT_SYMBOL(pagecache_write_end); + ssize_t generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, unsigned long *nr_segs, loff_t pos, loff_t *ppos, @@ -1886,8 +1984,7 @@ EXPORT_SYMBOL(generic_file_direct_write); * Find or create a page at the given pagecache position. Return the locked * page. This function is specifically for buffered writes. */ -static struct page *__grab_cache_page(struct address_space *mapping, - pgoff_t index) +struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index) { int status; struct page *page; @@ -1908,20 +2005,16 @@ repeat: } return page; } +EXPORT_SYMBOL(__grab_cache_page); -ssize_t -generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, - unsigned long nr_segs, loff_t pos, loff_t *ppos, - size_t count, ssize_t written) +static ssize_t generic_perform_write_2copy(struct file *file, + struct iov_iter *i, loff_t pos) { - struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; const struct address_space_operations *a_ops = mapping->a_ops; - struct inode *inode = mapping->host; - long status = 0; - struct iov_iter i; - - iov_iter_init(&i, iov, nr_segs, count, written); + struct inode *inode = mapping->host; + long status = 0; + ssize_t written = 0; do { struct page *src_page; @@ -1934,7 +2027,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, offset = (pos & (PAGE_CACHE_SIZE - 1)); index = pos >> PAGE_CACHE_SHIFT; bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, - iov_iter_count(&i)); + iov_iter_count(i)); /* * a non-NULL src_page indicates that we're doing the @@ -1952,7 +2045,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * to check that the address is actually valid, when atomic * usercopies are used, below. */ - if (unlikely(iov_iter_fault_in_readable(&i))) { + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { status = -EFAULT; break; } @@ -1983,7 +2076,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * same reason as we can't take a page fault with a * page locked (as explained below). */ - copied = iov_iter_copy_from_user(src_page, &i, + copied = iov_iter_copy_from_user(src_page, i, offset, bytes); if (unlikely(copied == 0)) { status = -EFAULT; @@ -2008,7 +2101,6 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, page_cache_release(src_page); continue; } - } status = a_ops->prepare_write(file, page, offset, offset+bytes); @@ -2030,7 +2122,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, * really matter. */ pagefault_disable(); - copied = iov_iter_copy_from_user_atomic(page, &i, + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); } else { @@ -2056,9 +2148,9 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, if (src_page) page_cache_release(src_page); - iov_iter_advance(&i, copied); - written += copied; + iov_iter_advance(i, copied); pos += copied; + written += copied; balance_dirty_pages_ratelimited(mapping); cond_resched(); @@ -2082,13 +2174,117 @@ fs_write_aop_error: continue; else break; - } while (iov_iter_count(&i)); - *ppos = pos; + } while (iov_iter_count(i)); + + return written ? written : status; +} + +static ssize_t generic_perform_write(struct file *file, + struct iov_iter *i, loff_t pos) +{ + struct address_space *mapping = file->f_mapping; + const struct address_space_operations *a_ops = mapping->a_ops; + long status = 0; + ssize_t written = 0; + + do { + struct page *page; + pgoff_t index; /* Pagecache index for current page */ + unsigned long offset; /* Offset into pagecache page */ + unsigned long bytes; /* Bytes to write to page */ + size_t copied; /* Bytes copied from user */ + void *fsdata; + + offset = (pos & (PAGE_CACHE_SIZE - 1)); + index = pos >> PAGE_CACHE_SHIFT; + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_count(i)); + +again: + + /* + * Bring in the user page that we will 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. + * + * Not only is this an optimisation, but it is also required + * to check that the address is actually valid, when atomic + * usercopies are used, below. + */ + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { + status = -EFAULT; + break; + } + + status = a_ops->write_begin(file, mapping, pos, bytes, 0, + &page, &fsdata); + if (unlikely(status)) + break; + + pagefault_disable(); + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); + pagefault_enable(); + flush_dcache_page(page); + + status = a_ops->write_end(file, mapping, pos, bytes, copied, + page, fsdata); + if (unlikely(status < 0)) + break; + copied = status; + + cond_resched(); + + if (unlikely(copied == 0)) { + /* + * If we were unable to copy any data at all, we must + * fall back to a single segment length write. + * + * If we didn't fallback here, we could livelock + * because not all segments in the iov can be copied at + * once without a pagefault. + */ + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_single_seg_count(i)); + goto again; + } + iov_iter_advance(i, copied); + pos += copied; + written += copied; + + balance_dirty_pages_ratelimited(mapping); + + } while (iov_iter_count(i)); + + return written ? written : status; +} + +ssize_t +generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, + unsigned long nr_segs, loff_t pos, loff_t *ppos, + size_t count, ssize_t written) +{ + struct file *file = iocb->ki_filp; + struct address_space *mapping = file->f_mapping; + const struct address_space_operations *a_ops = mapping->a_ops; + struct inode *inode = mapping->host; + ssize_t status; + struct iov_iter i; + + iov_iter_init(&i, iov, nr_segs, count, written); + if (a_ops->write_begin) + status = generic_perform_write(file, &i, pos); + else + status = generic_perform_write_2copy(file, &i, pos); - /* - * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC - */ if (likely(status >= 0)) { + written += status; + *ppos = pos + status; + + /* + * For now, when the user asks for O_SYNC, we'll actually give + * O_DSYNC + */ if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { if (!a_ops->writepage || !is_sync_kiocb(iocb)) status = generic_osync_inode(inode, mapping, |