Bug 202749 - f2fs: possibly fail to pageout because PagePrivate is set without increasing page count in .set_page_dirty()
Summary: f2fs: possibly fail to pageout because PagePrivate is set without increasing ...
Status: RESOLVED CODE_FIX
Alias: None
Product: File System
Classification: Unclassified
Component: f2fs (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: Default virtual assignee for f2fs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2019-03-04 14:23 UTC by Gao Xiang
Modified: 2019-03-18 09:34 UTC (History)
2 users (show)

See Also:
Kernel Version: 5.0 and older
Tree: Mainline
Regression: No


Attachments

Description Gao Xiang 2019-03-04 14:23:32 UTC
Hi,

It seems that f2fs sets PagePrivate in f2fs_set_data_page_dirty to indicate that it tend to enable corresponding .invalidatepage and .releasepage for these dirty pages.

However, it seems that it misses to add an extra page count when PagePrivate is set [1].

Therefore, I guess that it can cause that dirty pages are failed to pageout in some cases, therefore I changed mm/vmscan.c code to confirm my thought as follows:


diff --git a/mm/vmscan.c b/mm/vmscan.c
index b247e2c7bbc6..32ee664e686b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -642,8 +642,19 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
 	 * swap_backing_dev_info is bust: it doesn't reflect the
 	 * congestion state of the swapdevs.  Easy to fix, if needed.
 	 */
-	if (!is_page_cache_freeable(page))
+	if (!is_page_cache_freeable(page)) {
+		if (page_is_file_cache(page)) {
+			struct inode *const inode = page->mapping->host;
+
+			if (inode->i_sb->s_magic == F2FS_SUPER_MAGIC) {
+				if (PagePrivate(page)) {
+					printk(KERN_EMERG "gx: page %px inode %px page_private %lx count: %d\n", page, inode, page_private(page), page_count(page));
+					WARN_ON(1);
+				}
+			}
+		}
 		return PAGE_KEEP;
+	}
 	if (!mapping) {
 		/*
 		 * Some data journaling orphaned pages can have



with some fsstress pressures I got the following results:

...
[  123.545939] (3)[117:kswapd0]gx: page ffffffbf9638fe80 inode ffffffe57ea2c618 page_private 0 count: 2
[  123.545962] -(3)[117:kswapd0]------------[ cut here ]------------
[  123.545973] -(3)[117:kswapd0]WARNING: CPU: 3 PID: 117 at /home/g00380047/mt6761_2/kernel-4.9/mm/vmscan.c:652 shrink_page_list+0x5fc/0xddc
[  123.545980] -(3)[117:kswapd0]Modules linked in:
[  123.545990] -(3)[117:kswapd0]
[  123.546000] -(3)[117:kswapd0]CPU: 3 PID: 117 Comm: kswapd0 Tainted: G        W       4.9.117+ #144
[  123.546008] -(3)[117:kswapd0]Hardware name: MT6761V/WBB (DT)
[  123.546015] -(3)[117:kswapd0]task: ffffffe54ee68000 task.stack: ffffffe553158000
[  123.546023] -(3)[117:kswapd0]PC is at shrink_page_list+0x5fc/0xddc
[  123.546031] -(3)[117:kswapd0]LR is at shrink_page_list+0x5fc/0xddc
[  123.546038] -(3)[117:kswapd0]pc : [<ffffff84ce4065d4>] lr : [<ffffff84ce4065d4>] pstate: 60400145
--
[  123.549730] -(3)[117:kswapd0]b800: 0000000000000059 0000000000040975 0000000000040975 0000000000000001
[  123.549738] -(3)[117:kswapd0]b820: ffffff84d0068b68 ffffffe5bfebe050 0000000000008080 feff64716e73726f
[  123.549746] -(3)[117:kswapd0]b840: 7f7f7f7f7f7f7f7f 0000000000040975 0101010101010101 0000000000000030
[  123.549759] -(3)[117:kswapd0][<ffffff84ce4065d4>] shrink_page_list+0x5fc/0xddc
[  123.549768] -(3)[117:kswapd0][<ffffff84ce407770>] shrink_inactive_list+0x2e4/0x548
[  123.549777] -(3)[117:kswapd0][<ffffff84ce4084a0>] shrink_node_memcg.isra.77+0x7a0/0xad8
[  123.549784] -(3)[117:kswapd0][<ffffff84ce408838>] shrink_node+0x60/0x214
[  123.549792] -(3)[117:kswapd0][<ffffff84ce409438>] kswapd+0x36c/0x640
[  123.549803] -(3)[117:kswapd0][<ffffff84ce2d2164>] kthread+0xec/0x100
[  123.549812] -(3)[117:kswapd0][<ffffff84ce283d70>] ret_from_fork+0x10/0x20
[  123.549908] (3)[117:kswapd0]gx: page ffffffbf9638fec0 inode ffffffe57ea2c618 page_private 0 count: 2
[  123.549932] -(3)[117:kswapd0]------------[ cut here ]------------
[  123.549943] -(3)[117:kswapd0]WARNING: CPU: 3 PID: 117 at /home/g00380047/mt6761_2/kernel-4.9/mm/vmscan.c:652 shrink_page_list+0x5fc/0xddc
[  123.549951] -(3)[117:kswapd0]Modules linked in:
[  123.549960] -(3)[117:kswapd0]
[  123.549969] -(3)[117:kswapd0]CPU: 3 PID: 117 Comm: kswapd0 Tainted: G        W       4.9.117+ #144
[  123.549976] -(3)[117:kswapd0]Hardware name: MT6761V/WBB (DT)
[  123.549983] -(3)[117:kswapd0]task: ffffffe54ee68000 task.stack: ffffffe553158000
[  123.549991] -(3)[117:kswapd0]PC is at shrink_page_list+0x5fc/0xddc
[  123.549999] -(3)[117:kswapd0]LR is at shrink_page_list+0x5fc/0xddc
[  123.550006] -(3)[117:kswapd0]pc : [<ffffff84ce4065d4>] lr : [<ffffff84ce4065d4>] pstate: 60400145
--
[  123.553776] -(3)[117:kswapd0]b800: 0000000000000059 0000000000040975 0000000000040975 0000000000000001
[  123.553784] -(3)[117:kswapd0]b820: ffffff84d0068b68 ffffffe5bfebe050 0000000000008080 feff64716e73726f
[  123.553793] -(3)[117:kswapd0]b840: 7f7f7f7f7f7f7f7f 0000000000040975 0101010101010101 0000000000000030
[  123.553810] -(3)[117:kswapd0][<ffffff84ce4065d4>] shrink_page_list+0x5fc/0xddc
[  123.553818] -(3)[117:kswapd0][<ffffff84ce407770>] shrink_inactive_list+0x2e4/0x548
[  123.553827] -(3)[117:kswapd0][<ffffff84ce4084a0>] shrink_node_memcg.isra.77+0x7a0/0xad8
[  123.553835] -(3)[117:kswapd0][<ffffff84ce408838>] shrink_node+0x60/0x214
[  123.553842] -(3)[117:kswapd0][<ffffff84ce409438>] kswapd+0x36c/0x640
[  123.553853] -(3)[117:kswapd0][<ffffff84ce2d2164>] kthread+0xec/0x100
[  123.553863] -(3)[117:kswapd0][<ffffff84ce283d70>] ret_from_fork+0x10/0x20
[  123.556520] (3)[117:kswapd0]gx: page ffffffbf96385600 inode ffffffe57ea2c618 page_private 0 count: 2
[  123.556560] -(3)[117:kswapd0]------------[ cut here ]------------
[  123.556579] -(3)[117:kswapd0]WARNING: CPU: 3 PID: 117 at /home/g00380047/mt6761_2/kernel-4.9/mm/vmscan.c:652 shrink_page_list+0x5fc/0xddc
[  123.556587] -(3)[117:kswapd0]Modules linked in:
[  123.556599] -(3)[117:kswapd0]
[  123.556611] -(3)[117:kswapd0]CPU: 3 PID: 117 Comm: kswapd0 Tainted: G        W       4.9.117+ #144
[  123.556618] -(3)[117:kswapd0]Hardware name: MT6761V/WBB (DT)
[  123.556625] -(3)[117:kswapd0]task: ffffffe54ee68000 task.stack: ffffffe553158000
[  123.556634] -(3)[117:kswapd0]PC is at shrink_page_list+0x5fc/0xddc
[  123.556642] -(3)[117:kswapd0]LR is at shrink_page_list+0x5fc/0xddc
[  123.556650] -(3)[117:kswapd0]pc : [<ffffff84ce4065d4>] lr : [<ffffff84ce4065d4>] pstate: 60400145
--
[  123.560464] -(3)[117:kswapd0]b800: 0000000000000059 0000000000040975 0000000000040975 0000000000000001
[  123.560472] -(3)[117:kswapd0]b820: ffffff84d0068b68 ffffffe5bfebe050 0000000000008080 feff64716e73726f
[  123.560480] -(3)[117:kswapd0]b840: 7f7f7f7f7f7f7f7f 0000000000040975 0101010101010101 0000000000000030
[  123.560493] -(3)[117:kswapd0][<ffffff84ce4065d4>] shrink_page_list+0x5fc/0xddc
[  123.560502] -(3)[117:kswapd0][<ffffff84ce407770>] shrink_inactive_list+0x2e4/0x548
[  123.560511] -(3)[117:kswapd0][<ffffff84ce4084a0>] shrink_node_memcg.isra.77+0x7a0/0xad8
[  123.560518] -(3)[117:kswapd0][<ffffff84ce408838>] shrink_node+0x60/0x214
[  123.560527] -(3)[117:kswapd0][<ffffff84ce409438>] kswapd+0x36c/0x640
[  123.560537] -(3)[117:kswapd0][<ffffff84ce2d2164>] kthread+0xec/0x100
[  123.560547] -(3)[117:kswapd0][<ffffff84ce283d70>] ret_from_fork+0x10/0x20
...


and my random pressures generate from
1. echo 0 > /proc/sys/vm/swappiness
2. run 3 threads with
/data/fsstress -d /data/test -p 1000 -n 10000 -l0 -S -c
on my test low-end Android phone.


[1] for this constraint, see more details in
https://lore.kernel.org/lkml/2b19b3c4-2bc4-15fa-15cc-27a13e5c7af1@aol.com/
https://lore.kernel.org/lkml/583fba27-cbd7-1f90-8bf0-a3b49e75b0f6@huawei.com/


Thanks,
Gao Xiang
Comment 1 Gao Xiang 2019-03-18 08:25:53 UTC
mark as fixed.
Comment 2 Chao Yu 2019-03-18 09:34:13 UTC
For better bug track, attaching related fixing patch info as below:

240a59156d9b ("f2fs: fix to add refcount once page is tagged PG_private")

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=240a59156d9bcfabceddb66be449e7b32fb5dc4a

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