Commit 66d2f4d2 authored Jul 02, 2014 by Hugh Dickins Committed by Linus Torvalds Jul 03, 2014

shmem: fix init_page_accessed use to stop !PageLRU bug



Under shmem swapping load, I sometimes hit the VM_BUG_ON_PAGE(!PageLRU)
in isolate_lru_pages() at mm/vmscan.c:1281!

Commit 2457aec6 ("mm: non-atomically mark page accessed during page
cache allocation where possible") looks like interrupted work-in-progress.

mm/filemap.c's call to init_page_accessed() is fine, but not mm/shmem.c's
- shmem_write_begin() is clearly wrong to use it after shmem_getpage(),
when the page is always visible in radix_tree, and often already on LRU.

Revert change to shmem_write_begin(), and use init_page_accessed() or
mark_page_accessed() appropriately for SGP_WRITE in shmem_getpage_gfp().

SGP_WRITE also covers shmem_symlink(), which did not mark_page_accessed()
before; but since many other filesystems use [__]page_symlink(), which did
and does mark the page accessed, consider this as rectifying an oversight.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d18bbc21

mm/shmem.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -1029,6 +1029,9 @@ repeat:
		goto failed;
		}

		if (page && sgp == SGP_WRITE)
		mark_page_accessed(page);

		/* fallocated page? */
		if (page && !PageUptodate(page)) {
		if (sgp != SGP_READ)
		@@ -1110,6 +1113,9 @@ repeat:
		shmem_recalc_inode(inode);
		spin_unlock(&info->lock);

		if (sgp == SGP_WRITE)
		mark_page_accessed(page);

		delete_from_swap_cache(page);
		set_page_dirty(page);
		swap_free(swap);
		@@ -1136,6 +1142,9 @@ repeat:

		__SetPageSwapBacked(page);
		__set_page_locked(page);
		if (sgp == SGP_WRITE)
		init_page_accessed(page);

		error = mem_cgroup_charge_file(page, current->mm,
		gfp & GFP_RECLAIM_MASK);
		if (error)
		@@ -1412,13 +1421,9 @@ shmem_write_begin(struct file file, struct address_space mapping,
		loff_t pos, unsigned len, unsigned flags,
		struct page pagep, void fsdata)
		{
		int ret;
		struct inode *inode = mapping->host;
		pgoff_t index = pos >> PAGE_CACHE_SHIFT;
		ret = shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
		if (ret == 0 && *pagep)
		init_page_accessed(*pagep);
		return ret;
		return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
		}

		static int

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