Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org, Maxim Patlasov <maximvp@gmail.com>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] fuse_writepages_fill: simplified "if-else if" constuction
Date: Tue, 14 Jul 2020 14:24:33 +0200	[thread overview]
Message-ID: <CAJfpegv_7nvWoigY-eCX0ny+phWYOz3kEZvYsuGb=u65yMLGHg@mail.gmail.com> (raw)
In-Reply-To: <446f0df5-798d-ab3a-e773-39d9f202c092@virtuozzo.com>

[-- Attachment #1: Type: text/plain, Size: 545 bytes --]

On Thu, Jun 25, 2020 at 11:30 AM Vasily Averin <vvs@virtuozzo.com> wrote:
>
> fuse_writepages_fill uses following construction:
> if (wpa && ap->num_pages &&
>     (A || B || C)) {
>         action;
> } else if (wpa && D) {
>         if (E) {
>                 the same action;
>         }
> }
>
> - ap->num_pages check is always true and can be removed
> - "if" and "else if" calls the same action and can be merged.

Makes sense.  Attached patch goes further and moves checking the
conditions to a separate helper for clarity.

Thanks,
Miklos

[-- Attachment #2: fuse-clean-up-writepage-sending.patch --]
[-- Type: text/x-patch, Size: 3058 bytes --]

From: Miklos Szeredi <mszeredi@redhat.com>
Subject: fuse: clean up condition for writepage sending

fuse_writepages_fill uses following construction:

if (wpa && ap->num_pages &&
    (A || B || C)) {
        action;
} else if (wpa && D) {
        if (E) {
                the same action;
        }
}

 - ap->num_pages check is always true and can be removed

 - "if" and "else if" calls the same action and can be merged.

Move checking A, B, C, D, E conditions to a helper, add comments.

Original-patch-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/fuse/file.c |   51 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 33 insertions(+), 18 deletions(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2015,6 +2015,38 @@ static bool fuse_writepage_add(struct fu
 	return false;
 }
 
+static bool fuse_writepage_need_send(struct fuse_conn *fc, struct page *page,
+				     struct fuse_args_pages *ap,
+				     struct fuse_fill_wb_data *data)
+{
+	/*
+	 * Being under writeback is unlikely but possible.  For example direct
+	 * read to an mmaped fuse file will set the page dirty twice; once when
+	 * the pages are faulted with get_user_pages(), and then after the read
+	 * completed.
+	 */
+	if (fuse_page_is_writeback(data->inode, page->index))
+		return true;
+
+	/* Reached max pages */
+	if (ap->num_pages == fc->max_pages)
+		return true;
+
+	/* Reached max write bytes */
+	if ((ap->num_pages + 1) * PAGE_SIZE > fc->max_write)
+		return true;
+
+	/* Discontinuity */
+	if (data->orig_pages[ap->num_pages - 1]->index + 1 != page->index)
+		return true;
+
+	/* Need to grow the pages array?  If so, did the expansion fail? */
+	if (ap->num_pages == data->max_pages && !fuse_pages_realloc(data))
+		return true;
+
+	return false;
+}
+
 static int fuse_writepages_fill(struct page *page,
 		struct writeback_control *wbc, void *_data)
 {
@@ -2025,7 +2057,6 @@ static int fuse_writepages_fill(struct p
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct page *tmp_page;
-	bool is_writeback;
 	int err;
 
 	if (!data->ff) {
@@ -2035,25 +2066,9 @@ static int fuse_writepages_fill(struct p
 			goto out_unlock;
 	}
 
-	/*
-	 * Being under writeback is unlikely but possible.  For example direct
-	 * read to an mmaped fuse file will set the page dirty twice; once when
-	 * the pages are faulted with get_user_pages(), and then after the read
-	 * completed.
-	 */
-	is_writeback = fuse_page_is_writeback(inode, page->index);
-
-	if (wpa && ap->num_pages &&
-	    (is_writeback || ap->num_pages == fc->max_pages ||
-	     (ap->num_pages + 1) * PAGE_SIZE > fc->max_write ||
-	     data->orig_pages[ap->num_pages - 1]->index + 1 != page->index)) {
+	if (wpa && fuse_writepage_need_send(fc, page, ap, data)) {
 		fuse_writepages_send(data);
 		data->wpa = NULL;
-	} else if (wpa && ap->num_pages == data->max_pages) {
-		if (!fuse_pages_realloc(data)) {
-			fuse_writepages_send(data);
-			data->wpa = NULL;
-		}
 	}
 
 	err = -ENOMEM;

  reply	other threads:[~2020-07-14 12:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <2733b41a-b4c6-be94-0118-a1a8d6f26eec@virtuozzo.com>
2020-06-25  9:02 ` [PATCH] fuse_writepages_fill() optimization to avoid WARN_ON in tree_insert Vasily Averin
2020-06-27 10:31   ` Sedat Dilek
2020-06-29 21:11   ` Vivek Goyal
2020-07-11  4:01   ` Miklos Szeredi
2020-07-13  8:02     ` Vasily Averin
2020-07-13 16:14       ` Miklos Szeredi
2020-07-14  6:18         ` Vasily Averin
2020-07-14 12:40         ` Sedat Dilek
2020-07-14 12:52           ` Miklos Szeredi
2020-07-14 12:57             ` Sedat Dilek
2020-07-15  7:48               ` Sedat Dilek
2020-06-25  9:30 ` [PATCH] fuse_writepages_fill: simplified "if-else if" constuction Vasily Averin
2020-07-14 12:24   ` Miklos Szeredi [this message]
2020-07-14 18:53     ` Vasily Averin
2020-06-25  9:39 ` [PATCH] fuse_writepages ignores errors from fuse_writepages_fill Vasily Averin
2020-07-14 12:44   ` Miklos Szeredi

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAJfpegv_7nvWoigY-eCX0ny+phWYOz3kEZvYsuGb=u65yMLGHg@mail.gmail.com' \
    --to=miklos@szeredi.hu \
    --cc=ktkhai@virtuozzo.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=maximvp@gmail.com \
    --cc=vvs@virtuozzo.com \
    --subject='Re: [PATCH] fuse_writepages_fill: simplified "if-else if" constuction' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).