On Sat, Mar 25, 2017 at 07:49:00AM +0000, Ivan Kozik wrote: > Hi, > > I would like to request that this patch be included in the 4.4 stable tree. It > fixes the Bad page state issue discovered at > http://oss.sgi.com/archives/xfs/2016-08/msg00617.html ('"Bad page state" errors > when calling BULKSTAT under memory pressure?') > > I tested the patch (no changes needed) by applying it to 4.4.52, running a > program to use almost all of my free memory, then running xfs_fsr on a > filesystem with > 1.5M files. Before patch: kernel screams with Bad page state > / "count:-1" within a minute. After patch: no complaints from the kernel. > I repeated the test several times and on another machine that was affected. > I have not seen any problems five days later. FWIW this looks fine for 4.4, so Acked-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> (It's probably ok for all the stable kernels too, but I haven't tested any of them so I won't make such a claim at this time.) --D > > Thanks, > > Ivan > > >From 2aa6ba7b5ad3189cc27f14540aa2f57f0ed8df4b Mon Sep 17 00:00:00 2001 > From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx> > Date: Wed, 25 Jan 2017 20:24:57 -0800 > Subject: [PATCH] xfs: clear _XBF_PAGES from buffers when readahead page > > If we try to allocate memory pages to back an xfs_buf that we're trying > to read, it's possible that we'll be so short on memory that the page > allocation fails. For a blocking read we'll just wait, but for > readahead we simply dump all the pages we've collected so far. > > Unfortunately, after dumping the pages we neglect to clear the > _XBF_PAGES state, which means that the subsequent call to xfs_buf_free > thinks that b_pages still points to pages we own. It then double-frees > the b_pages pages. > > This results in screaming about negative page refcounts from the memory > manager, which xfs oughtn't be triggering. To reproduce this case, > mount a filesystem where the size of the inodes far outweighs the > availalble memory (a ~500M inode filesystem on a VM with 300MB memory > did the trick here) and run bulkstat in parallel with other memory > eating processes to put a huge load on the system. The "check summary" > phase of xfs_scrub also works for this purpose. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx> > --- > fs/xfs/xfs_buf.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c > index 7f0a01f7b592..ac3b4db519df 100644 > --- a/fs/xfs/xfs_buf.c > +++ b/fs/xfs/xfs_buf.c > @@ -422,6 +422,7 @@ retry: > out_free_pages: > for (i = 0; i < bp->b_page_count; i++) > __free_page(bp->b_pages[i]); > + bp->b_flags &= ~_XBF_PAGES; > return error; > } > > -- > 2.11.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html