From 0b8def9d6dfa6b2a9a2740cf81d8d2c134688d39 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 7 Apr 2015 10:22:53 -0400 Subject: __generic_file_write_iter: keep ->ki_pos and return value consistent A side effect worth noting: in O_APPEND case we set ->ki_pos early, so if it turns out to be an error or a zero-length write, we'll end up with ->ki_pos modified. Safe, since all callers never look at the ->ki_pos after the call of __generic_file_write_iter() returning non-positive, all the way to caller of ->write_iter() and those discard ->ki_pos when getting that. Signed-off-by: Al Viro --- mm/filemap.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index 9920db455f05..353f82e09e63 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2557,7 +2557,6 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) struct file *file = iocb->ki_filp; struct address_space * mapping = file->f_mapping; struct inode *inode = mapping->host; - loff_t pos = iocb->ki_pos; ssize_t written = 0; ssize_t err; ssize_t status; @@ -2565,7 +2564,7 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) /* We can write back this queue in page reclaim */ current->backing_dev_info = inode_to_bdi(inode); - err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); + err = generic_write_checks(file, &iocb->ki_pos, &count, S_ISBLK(inode->i_mode)); if (err) goto out; @@ -2583,9 +2582,9 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) goto out; if (io_is_direct(file)) { - loff_t endbyte; + loff_t pos, endbyte; - written = generic_file_direct_write(iocb, from, pos); + written = generic_file_direct_write(iocb, from, iocb->ki_pos); /* * If the write stopped short of completing, fall back to * buffered writes. Some filesystems do this for writes to @@ -2593,13 +2592,10 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) * not succeed (even if it did, DAX does not handle dirty * page-cache pages correctly). */ - if (written < 0 || written == count || IS_DAX(inode)) + if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) goto out; - pos += written; - count -= written; - - status = generic_perform_write(file, from, pos); + status = generic_perform_write(file, from, pos = iocb->ki_pos); /* * If generic_perform_write() returned a synchronous error * then we want to return the number of bytes which were @@ -2611,15 +2607,15 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) err = status; goto out; } - iocb->ki_pos = pos + status; /* * We need to ensure that the page cache pages are written to * disk and invalidated to preserve the expected O_DIRECT * semantics. */ endbyte = pos + status - 1; - err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte); + err = filemap_write_and_wait_range(mapping, pos, endbyte); if (err == 0) { + iocb->ki_pos = endbyte + 1; written += status; invalidate_mapping_pages(mapping, pos >> PAGE_CACHE_SHIFT, @@ -2631,9 +2627,9 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) */ } } else { - written = generic_perform_write(file, from, pos); - if (likely(written >= 0)) - iocb->ki_pos = pos + written; + written = generic_perform_write(file, from, iocb->ki_pos); + if (likely(written > 0)) + iocb->ki_pos += written; } out: current->backing_dev_info = NULL; -- cgit v1.2.3-59-g8ed1b