From 1da6589d327fdfbb2c91551ea9047e598b4115f5 Mon Sep 17 00:00:00 2001 From: Sunghan Suh Date: Wed, 3 Jul 2013 20:10:05 +0900 Subject: [PATCH] zram: prevent data loss in error cases of function zram_bvec_write() In function zram_bvec_write(), previous data at the index is already freed by function zram_free_page(). When failed to compress or zs_malloc, there is no way to restore old data. Therefore, free previous data when it's about to update. Also, no need to check whether table is not empty outside of function zram_free_page(), because the function properly checks inside. Signed-off-by: Sunghan Suh Signed-off-by: Greg Kroah-Hartman (cherry picked from commit f40ac2ae1b506484dd9261a24bbf3e86b2206ff8) Signed-off-by: Alex Shi --- drivers/staging/zram/zram_drv.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 77f40a7a6726..84df3999d6af 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -418,14 +418,6 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, goto out; } - /* - * System overwrites unused sectors. Free memory associated - * with this sector now. - */ - if (meta->table[index].handle || - zram_test_flag(meta, index, ZRAM_ZERO)) - zram_free_page(zram, index); - user_mem = kmap_atomic(page); if (is_partial_io(bvec)) { @@ -439,6 +431,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, if (page_zero_filled(uncmem)) { kunmap_atomic(user_mem); + /* Free memory associated with this sector now. */ + zram_free_page(zram, index); + zram->stats.pages_zero++; zram_set_flag(meta, index, ZRAM_ZERO); ret = 0; @@ -486,6 +481,12 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, zs_unmap_object(meta->mem_pool, handle); + /* + * Free memory associated with this sector + * before overwriting unused sectors. + */ + zram_free_page(zram, index); + meta->table[index].handle = handle; meta->table[index].size = clen; -- 2.34.1