Linux-Block Archive on lore.kernel.org
 help / color / Atom feed
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Cc: stable@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH v2] loop: avoid EAGAIN, if offset or block_size are changed
Date: Fri, 17 May 2019 17:53:04 -0700
Message-ID: <20190518005304.GA19446@jaegeuk-macbookpro.roam.corp.google.com> (raw)
In-Reply-To: <20190518004751.18962-1-jaegeuk@kernel.org>

This patch tries to avoid EAGAIN due to nrpages!=0 that was originally trying
to drop stale pages resulting in wrong data access.

Report: https://bugs.chromium.org/p/chromium/issues/detail?id=938958#c38

Cc: <stable@vger.kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: Bart Van Assche <bvanassche@acm.org>
Fixes: 5db470e229e2 ("loop: drop caches if offset or block_size are changed")
Reported-by: Gwendal Grignou <gwendal@chromium.org>
Reported-by: grygorii tertychnyi <gtertych@cisco.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
v2 from v1:
 - remove obsolete jump

 drivers/block/loop.c | 45 +++++++++++++++++---------------------------
 1 file changed, 17 insertions(+), 28 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 102d79575895..42994de2dd12 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1212,6 +1212,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 	kuid_t uid = current_uid();
 	struct block_device *bdev;
 	bool partscan = false;
+	bool drop_caches = false;
 
 	err = mutex_lock_killable(&loop_ctl_mutex);
 	if (err)
@@ -1232,10 +1233,8 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 	}
 
 	if (lo->lo_offset != info->lo_offset ||
-	    lo->lo_sizelimit != info->lo_sizelimit) {
-		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
-	}
+	    lo->lo_sizelimit != info->lo_sizelimit)
+		drop_caches = true;
 
 	/* I/O need to be drained during transfer transition */
 	blk_mq_freeze_queue(lo->lo_queue);
@@ -1265,14 +1264,6 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 
 	if (lo->lo_offset != info->lo_offset ||
 	    lo->lo_sizelimit != info->lo_sizelimit) {
-		/* kill_bdev should have truncated all the pages */
-		if (lo->lo_device->bd_inode->i_mapping->nrpages) {
-			err = -EAGAIN;
-			pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
-				__func__, lo->lo_number, lo->lo_file_name,
-				lo->lo_device->bd_inode->i_mapping->nrpages);
-			goto out_unfreeze;
-		}
 		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
 			err = -EFBIG;
 			goto out_unfreeze;
@@ -1317,6 +1308,12 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 		bdev = lo->lo_device;
 		partscan = true;
 	}
+
+	/* truncate stale pages cached by previous operations */
+	if (!err && drop_caches) {
+		sync_blockdev(lo->lo_device);
+		kill_bdev(lo->lo_device);
+	}
 out_unlock:
 	mutex_unlock(&loop_ctl_mutex);
 	if (partscan)
@@ -1498,6 +1495,7 @@ static int loop_set_dio(struct loop_device *lo, unsigned long arg)
 
 static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 {
+	bool drop_caches = false;
 	int err = 0;
 
 	if (lo->lo_state != Lo_bound)
@@ -1506,30 +1504,21 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 	if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
 		return -EINVAL;
 
-	if (lo->lo_queue->limits.logical_block_size != arg) {
-		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
-	}
+	if (lo->lo_queue->limits.logical_block_size != arg)
+		drop_caches = true;
 
 	blk_mq_freeze_queue(lo->lo_queue);
-
-	/* kill_bdev should have truncated all the pages */
-	if (lo->lo_queue->limits.logical_block_size != arg &&
-			lo->lo_device->bd_inode->i_mapping->nrpages) {
-		err = -EAGAIN;
-		pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
-			__func__, lo->lo_number, lo->lo_file_name,
-			lo->lo_device->bd_inode->i_mapping->nrpages);
-		goto out_unfreeze;
-	}
-
 	blk_queue_logical_block_size(lo->lo_queue, arg);
 	blk_queue_physical_block_size(lo->lo_queue, arg);
 	blk_queue_io_min(lo->lo_queue, arg);
 	loop_update_dio(lo);
-out_unfreeze:
 	blk_mq_unfreeze_queue(lo->lo_queue);
 
+	/* truncate stale pages cached by previous operations */
+	if (drop_caches) {
+		sync_blockdev(lo->lo_device);
+		kill_bdev(lo->lo_device);
+	}
 	return err;
 }
 
-- 
2.19.0.605.g01d371f741-goog


  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-18  0:47 [PATCH] " Jaegeuk Kim
2019-05-18  0:53 ` Jaegeuk Kim [this message]
2019-06-17 21:08   ` [f2fs-dev] [PATCH v2] " Jaegeuk Kim
2019-06-10 21:49 [PATCH v2] loop: avoid EAGAIN, if offset or block size " fruggeri

Reply instructions:

You may reply publically 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=20190518005304.GA19446@jaegeuk-macbookpro.roam.corp.google.com \
    --to=jaegeuk@kernel.org \
    --cc=axboe@kernel.dk \
    --cc=bvanassche@acm.org \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-kernel@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    /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

Linux-Block Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-block/0 linux-block/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-block linux-block/ https://lore.kernel.org/linux-block \
		linux-block@vger.kernel.org linux-block@archiver.kernel.org
	public-inbox-index linux-block


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-block


AGPL code for this site: git clone https://public-inbox.org/ public-inbox