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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, NeilBrown <neilb@suse.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 47/96] staging: lustre: fix bug in osc_enter_cache_try
Date:   Thu, 24 May 2018 11:38:30 +0200
Message-Id: <20180524093608.182210250@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@suse.com>

[ Upstream commit 2fab9faf9b27298c4536c1c1b14072ab18b8f80b ]

The lustre-release patch commit bdc5bb52c554 ("LU-4933 osc:
Automatically increase the max_dirty_mb") changed

-       if (cli->cl_dirty + PAGE_CACHE_SIZE <= cli->cl_dirty_max &&
+       if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&

When this patch landed in Linux a couple of years later, it landed as

-       if (cli->cl_dirty + PAGE_SIZE <= cli->cl_dirty_max &&
+       if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&

which is clearly different ('<=' vs '<'), and allows cl_dirty_pages to
increase beyond cl_dirty_max_pages - which causes a latter assertion
to fails.

Fixes: 3147b268400a ("staging: lustre: osc: Automatically increase the max_dirty_mb")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/lustre/lustre/include/obd.h   |    2 +-
 drivers/staging/lustre/lustre/osc/osc_cache.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/staging/lustre/lustre/include/obd.h
+++ b/drivers/staging/lustre/lustre/include/obd.h
@@ -253,7 +253,7 @@ struct client_obd {
 	struct sptlrpc_flavor    cl_flvr_mgc;   /* fixed flavor of mgc->mgs */
 
 	/* the grant values are protected by loi_list_lock below */
-	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pahges */
+	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pages */
 	unsigned long		 cl_dirty_max_pages;	/* allowed w/o rpc */
 	unsigned long		 cl_dirty_transit;	/* dirty synchronous */
 	unsigned long		 cl_avail_grant;	/* bytes of credit for ost */
--- a/drivers/staging/lustre/lustre/osc/osc_cache.c
+++ b/drivers/staging/lustre/lustre/osc/osc_cache.c
@@ -1542,7 +1542,7 @@ static int osc_enter_cache_try(struct cl
 	if (rc < 0)
 		return 0;
 
-	if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&
+	if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&
 	    atomic_long_read(&obd_dirty_pages) + 1 <= obd_max_dirty_pages) {
 		osc_consume_write_grant(cli, &oap->oap_brw_page);
 		if (transient) {