From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-112.freemail.mail.aliyun.com (out30-112.freemail.mail.aliyun.com [115.124.30.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 81C6F1FAF17 for ; Wed, 16 Oct 2024 10:09:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.112 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729073391; cv=none; b=Z8Pw69rHlVk6ZTfOCmbiCj48EaWdw8Td7zeYBGWGWLNyF5wK8Q2dKd7wUhEuxFYKmyJE01ni/BTccZG3f19dOO3vRd7xrSgLNIHTNstD587pbbsWMI1IR+b9rv0FqBzZlZ0vM8eW9DR6NmpWqsnHz8IlghV5/pZgAwHohw09gYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729073391; c=relaxed/simple; bh=G4q1nSaHcdhW8W+lBVsXIlaXABlbvqzyjc6WgN4XtXM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Mu/TJ2JW4k0Gpbi4qRe7zstAyc/MoA1c9tBZuP7KO1aA7R8nlPmG/XVAOuyIE2y1gNDi8mGHPvVMNW8yV6vHDBQiWfWu244yhecPIHD2zU/m0S8AH8uyzI7ieizywWfzAT6wE4/gNaROCLNaRWhiSHvqlODRBw6HLXe5IQFaV5k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=RtkwtDPA; arc=none smtp.client-ip=115.124.30.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="RtkwtDPA" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1729073379; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=45jXNMOMveZfimQ7xMKpnxhxl+Z6GR9GWhFQh6xPUvM=; b=RtkwtDPA5zNK7X9fng3o5Z0AbVRyNRYkIWBdIP27cDWFoo9q5cVei7/drfUUt7542fOUa+QVg9eRX6nE86wFLJnEhmiq0Tw2/TmW2mvLzhA9S1cpzMnS8kbyPoU8k0NlpzXwIHodBX8300kPAYoS+Zp5+6Eq6U5HtfxFsJpFOgA= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WHH-UDB_1729073378 cluster:ay36) by smtp.aliyun-inc.com; Wed, 16 Oct 2024 18:09:39 +0800 From: Baolin Wang To: akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, david@redhat.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mm: shmem: update iocb->ki_pos directly to simplify tmpfs read logic Date: Wed, 16 Oct 2024 18:09:29 +0800 Message-Id: X-Mailer: git-send-email 2.39.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Use iocb->ki_pos to check if the read bytes exceeds the file size and to calculate the bytes to be read can help simplify the code logic. Meanwhile, this is also a preparation for improving tmpfs large folios read performace in the following patch. Signed-off-by: Baolin Wang --- mm/shmem.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 66eae800ffab..edab02a26aac 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3106,26 +3106,18 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) unsigned long offset; int error = 0; ssize_t retval = 0; - loff_t *ppos = &iocb->ki_pos; - index = *ppos >> PAGE_SHIFT; - offset = *ppos & ~PAGE_MASK; + index = iocb->ki_pos >> PAGE_SHIFT; + offset = iocb->ki_pos & ~PAGE_MASK; for (;;) { struct folio *folio = NULL; struct page *page = NULL; - pgoff_t end_index; unsigned long nr, ret; - loff_t i_size = i_size_read(inode); + loff_t end_offset, i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index > end_index) + if (unlikely(iocb->ki_pos >= i_size)) break; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) - break; - } error = shmem_get_folio(inode, index, 0, &folio, SGP_READ); if (error) { @@ -3148,18 +3140,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * We must evaluate after, since reads (unlike writes) * are called without i_rwsem protection against truncate */ - nr = PAGE_SIZE; i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) { - if (folio) - folio_put(folio); - break; - } + if (unlikely(iocb->ki_pos >= i_size)) { + if (folio) + folio_put(folio); + break; } - nr -= offset; + end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); + nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset); if (folio) { /* @@ -3199,8 +3187,9 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) retval += ret; offset += ret; - index += offset >> PAGE_SHIFT; offset &= ~PAGE_MASK; + iocb->ki_pos += ret; + index = iocb->ki_pos >> PAGE_SHIFT; if (!iov_iter_count(to)) break; @@ -3211,7 +3200,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) cond_resched(); } - *ppos = ((loff_t) index << PAGE_SHIFT) + offset; file_accessed(file); return retval ? retval : error; } -- 2.39.3