On Wed, Jan 11, 2017 at 10:00:19AM +0100, Jan Kara wrote: > Commit 99579ccec4e2 "xfs: skip dirty pages in ->releasepage()" started > to skip dirty pages in xfs_vm_releasepage() which also has the effect > that if a dirty page is truncated, it does not get freed by > block_invalidatepage() and is lingering in LRU list waiting for reclaim. > So a simple loop like: > > while true; do > dd if=/dev/zero of=file bs=1M count=100 > rm file > done > > will keep using more and more memory until we hit low watermarks and > start pagecache reclaim which will eventually reclaim also the truncate > pages. Keeping these truncated (and thus never usable) pages in memory > is just a waste of memory, is unnecessarily stressing page cache > reclaim, and reportedly also leads to anonymous mmap(2) returning ENOMEM > prematurely. > > So instead of just skipping dirty pages in xfs_vm_releasepage(), return > to old behavior of skipping them only if they have delalloc or unwritten > buffers and fix the spurious warnings by warning only if the page is > clean. > > CC: stable@xxxxxxxxxxxxxxx > CC: Brian Foster <bfoster@xxxxxxxxxx> > CC: Vlastimil Babka <vbabka@xxxxxxx> > Reported-by: Petr Tůma <petr.tuma@xxxxxxxxxxxxxxx> > Fixes: 99579ccec4e271c3d4d4e7c946058766812afdab > Signed-off-by: Jan Kara <jack@xxxxxxx> > --- Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> > fs/xfs/xfs_aops.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 0f56fcd3a5d5..631e7c0e0a29 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -1152,19 +1152,22 @@ xfs_vm_releasepage( > * block_invalidatepage() can send pages that are still marked dirty > * but otherwise have invalidated buffers. > * > - * We've historically freed buffers on the latter. Instead, quietly > - * filter out all dirty pages to avoid spurious buffer state warnings. > - * This can likely be removed once shrink_active_list() is fixed. > + * We want to release the latter to avoid unnecessary buildup of the > + * LRU, skip the former and warn if we've left any lingering > + * delalloc/unwritten buffers on clean pages. Skip pages with delalloc > + * or unwritten buffers and warn if the page is not dirty. Otherwise > + * try to release the buffers. > */ > - if (PageDirty(page)) > - return 0; > - > xfs_count_page_state(page, &delalloc, &unwritten); > > - if (WARN_ON_ONCE(delalloc)) > + if (delalloc) { > + WARN_ON_ONCE(!PageDirty(page)); > return 0; > - if (WARN_ON_ONCE(unwritten)) > + } > + if (unwritten) { > + WARN_ON_ONCE(!PageDirty(page)); > return 0; > + } > > return try_to_free_buffers(page); > } > -- > 2.10.2 > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html