The patch titled
Subject: zram: keep the exact overcommited value in mem_used_max
has been added to the -mm tree. Its filename is
zram-keep-the-exact-overcommited-value-in-mem_used_max.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-keep-the-exact-overcommited-value-in-mem_used_max.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-keep-the-exact-overcommited-value-in-mem_used_max.patch
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From: Sergey SENOZHATSKY <sergey.senozhatsky@xxxxxxxxx>
Subject: zram: keep the exact overcommited value in mem_used_max
`mem_used_max' is designed to store the max amount of memory zram consumed
to store the data. However, it does not represent the actual
'overcommited' (max) value. The existing code goes to -ENOMEM
overcommited case before it updates `->stats.max_used_pages', which hides
the reason we went to -ENOMEM in the first place -- we actually used more
memory than `->limit_pages':
alloced_pages = zs_get_total_pages(meta->mem_pool);
if (zram->limit_pages && alloced_pages > zram->limit_pages) {
zs_free(meta->mem_pool, handle);
ret = -ENOMEM;
goto out;
}
update_used_max(zram, alloced_pages);
Which is misleading. User will see -ENOMEM, check `->limit_pages', check
`->stats.max_used_pages', which will keep the value BEFORE zram passed
`->limit_pages', and see:
`->stats.max_used_pages' < `->limit_pages'
Move update_used_max() before we do `->limit_pages' check, so that
user will see:
`->stats.max_used_pages' > `->limit_pages'
should the overcommit and -ENOMEM happen.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN drivers/block/zram/zram_drv.c~zram-keep-the-exact-overcommited-value-in-mem_used_max drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-keep-the-exact-overcommited-value-in-mem_used_max
+++ a/drivers/block/zram/zram_drv.c
@@ -726,14 +726,14 @@ static int zram_bvec_write(struct zram *
}
alloced_pages = zs_get_total_pages(meta->mem_pool);
+ update_used_max(zram, alloced_pages);
+
if (zram->limit_pages && alloced_pages > zram->limit_pages) {
zs_free(meta->mem_pool, handle);
ret = -ENOMEM;
goto out;
}
- update_used_max(zram, alloced_pages);
-
cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
_
Patches currently in -mm which might be from sergey.senozhatsky@xxxxxxxxx are
zram-keep-the-exact-overcommited-value-in-mem_used_max.patch
zram-update-documentation.patch
mm-zsmalloc-constify-struct-zs_pool-name.patch
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