From: Luis Chamberlain <mcgrof@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-xfs@vger.kernel.org, Dave Chinner <david@fromorbit.com>,
Brian Foster <bfoster@redhat.com>
Subject: Re: [PATCH] fs: xfs: xfs_log: Don't use KM_MAYFAIL at xfs_log_reserve().
Date: Thu, 1 Aug 2019 18:50:57 +0000 [thread overview]
Message-ID: <20190801185057.GT30113@42.do-not-panic.com> (raw)
In-Reply-To: <1564653995-9004-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
On Thu, Aug 01, 2019 at 07:06:35PM +0900, Tetsuo Handa wrote:
> When the system is close-to-OOM, fsync() may fail due to -ENOMEM because
> xfs_log_reserve() is using KM_MAYFAIL. It is a bad thing to fail writeback
> operation due to user-triggerable OOM condition. Since we are not using
> KM_MAYFAIL at xfs_trans_alloc() before calling xfs_log_reserve(), let's
> use the same flags at xfs_log_reserve().
>
> oom-torture: page allocation failure: order:0, mode:0x46c40(GFP_NOFS|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_COMP), nodemask=(null)
> CPU: 7 PID: 1662 Comm: oom-torture Kdump: loaded Not tainted 5.3.0-rc2+ #925
> Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00
> Call Trace:
> dump_stack+0x67/0x95
> warn_alloc+0xa9/0x140
> __alloc_pages_slowpath+0x9a8/0xbce
> __alloc_pages_nodemask+0x372/0x3b0
> alloc_slab_page+0x3a/0x8d0
> new_slab+0x330/0x420
> ___slab_alloc.constprop.94+0x879/0xb00
> __slab_alloc.isra.89.constprop.93+0x43/0x6f
> kmem_cache_alloc+0x331/0x390
> kmem_zone_alloc+0x9f/0x110 [xfs]
> kmem_zone_alloc+0x9f/0x110 [xfs]
> xlog_ticket_alloc+0x33/0xd0 [xfs]
> xfs_log_reserve+0xb4/0x410 [xfs]
> xfs_trans_reserve+0x1d1/0x2b0 [xfs]
> xfs_trans_alloc+0xc9/0x250 [xfs]
> xfs_setfilesize_trans_alloc.isra.27+0x44/0xc0 [xfs]
> xfs_submit_ioend.isra.28+0xa5/0x180 [xfs]
> xfs_vm_writepages+0x76/0xa0 [xfs]
> do_writepages+0x17/0x80
> __filemap_fdatawrite_range+0xc1/0xf0
> file_write_and_wait_range+0x53/0xa0
> xfs_file_fsync+0x87/0x290 [xfs]
> vfs_fsync_range+0x37/0x80
> do_fsync+0x38/0x60
> __x64_sys_fsync+0xf/0x20
> do_syscall_64+0x4a/0x1c0
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
That's quite an opaque commit log for what started off as a severe email
thread of potential leak of information. As such, can you expand on this
commit log considerably to explain the situation a bit better? Your
initial thread here provided much clearer evidence of the issue. As-is
this commit log tells the reader *nothing* about the potential harm in
not applying this patch.
You had mentioned you identified this issue present on at least
4.18 till 5.3-rc1. So, I'm at least inclined to consider this for
stable for at least v4.19.
However, what about older kernels? Now that you have identified
a fix, were the flag changed in prior commits, is it a regression
that perhaps added KM_MAYFAIL at some point?
Luis
next prev parent reply other threads:[~2019-08-01 18:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 10:06 xfs: garbage file data inclusion bug under memory pressure Tetsuo Handa
2019-07-25 10:53 ` Brian Foster
2019-07-25 12:30 ` Tetsuo Handa
2019-07-25 16:00 ` Brian Foster
2019-07-25 11:32 ` Dave Chinner
2019-07-25 12:44 ` Tetsuo Handa
2019-07-25 17:28 ` Darrick J. Wong
2019-07-25 22:07 ` Dave Chinner
2019-07-29 3:50 ` Tetsuo Handa
2019-07-29 11:23 ` Brian Foster
2019-07-29 21:56 ` Dave Chinner
2019-07-30 11:30 ` Brian Foster
2019-08-01 10:06 ` [PATCH] fs: xfs: xfs_log: Don't use KM_MAYFAIL at xfs_log_reserve() Tetsuo Handa
2019-08-01 10:56 ` Brian Foster
2019-08-01 11:00 ` Tetsuo Handa
2019-08-01 18:50 ` Luis Chamberlain [this message]
2019-08-01 20:46 ` Darrick J. Wong
2019-08-02 22:21 ` Luis Chamberlain
2019-08-12 10:57 ` Tetsuo Handa
2019-08-12 19:55 ` Darrick J. Wong
2019-08-01 21:13 ` Tetsuo Handa
2019-08-01 21:55 ` Dave Chinner
2019-08-01 20:46 ` Darrick J. Wong
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