linux-kernel - nfs: wrong function to increment NFSIOS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 24 Mar 2015 20:53:16 +0800
From:	Nicolas Iooss <nicolas.iooss_linux@....org>
To:	Li RongQing <roy.qing.li@...il.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Anna Schumaker <anna.schumaker@...app.com>
CC:	linux-nfs@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: nfs: wrong function to increment NFSIOS_READPAGES/WRITEPAGES stat
 counters?

Hello,

Since commit 5a254d08b086 ("nfs: replace nfs_add_stats with
nfs_inc_stats when add one") [1], nfs_readpage and nfs_do_writepage  use
nfs_inc_stats to increment NFSIOS_READPAGES and NFSIOS_WRITEPAGES
instead of nfs_add_stats.

However nfs_inc_stats is not similar as nfs_add_stats with parameter 1
because these functions work on distinct stats:
nfs_inc_stats increments stats from "enum nfs_stat_eventcounters" (in
server->io_stats->events) and nfs_add_stats those from "enum
nfs_stat_bytecounters" (in server->io_stats->bytes), according to their
implementations in fs/nfs/iostat.h [2].

If I understand the code correctly, "nfs_inc_stats(inode,
NFSIOS_READPAGES);" is in fact executed as "nfs_inc_stats(inode,
NFSIOS_VFSACCESS);" and "nfs_inc_stats(inode, NFSIOS_WRITEPAGES);" as
"nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);".

As this looks like a bug to me, I am reporting it in hope it could be
fixed, for example by reverting 5a254d08b086.  Of course, I may be
wrong, in which case an explanation about what I missed in my analysis
would be appreciated.

By the way, I found this while trying to compile LLVMLinux on current
master branch of Linux.  clang reported the following warnings:

fs/nfs/read.c:287:23: warning: implicit conversion from enumeration type
'enum nfs_stat_bytecounters' to different enumeration type 'enum
nfs_stat_eventcounters' [-Wenum-conversion]
            nfs_inc_stats(inode, NFSIOS_READPAGES);
            ~~~~~~~~~~~~~        ^~~~~~~~~~~~~~~~

fs/nfs/write.c:583:23: warning: implicit conversion from enumeration
type 'enum nfs_stat_bytecounters' to different enumeration type 'enum
nfs_stat_eventcounters' [-Wenum-conversion]
            nfs_inc_stats(inode, NFSIOS_WRITEPAGES);
            ~~~~~~~~~~~~~        ^~~~~~~~~~~~~~~~~

Thanks,

Nicolas

[1]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=5a254d08b086d80cbead2ebcee6d2a4b3a15587a
[2]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/nfs/iostat.h?id=90a5a895cc8b284ac522757a01de15e36710c2b9
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/