Under shmem swapping load, I sometimes hit the VM_BUG_ON_PAGE(!PageLRU)
in isolate_lru_pages() at mm/vmscan.c:1281!
Commit 2457aec63745 ("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 <hu...@google.com>
---
mm/shmem.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
--- 3.16-rc3/mm/shmem.c 2014-06-29 15:22:10.592003936 -0700
+++ linux/mm/shmem.c 2014-06-30 12:15:52.204093217 -0700
@@ -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, str
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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