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Subject[PATCH] [staging][zram] Fix handling of incompressible pages
Date
Change 130f315a introduced a bug in the handling of incompressible
pages which resulted in memory allocation failure for such pages.
The fix is to store the page as-is i.e. without compression if the
compressed size exceeds a threshold (max_zpage_size) and request
exactly PAGE_SIZE sized buffer from zsmalloc.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Reported-by: viechweg@gmail.com
Reported-by: paerley@gmail.com
Reported-by: wu.tommy@gmail.com
Tested-by: wu.tommy@gmail.com
Tested-by: michael@zugelder.org
---
drivers/staging/zram/zram_drv.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 653b074..6edefde 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -223,8 +223,13 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
cmem = zs_map_object(zram->mem_pool, zram->table[index].handle,
ZS_MM_RO);

- ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
+ if (zram->table[index].size == PAGE_SIZE) {
+ memcpy(uncmem, cmem, PAGE_SIZE);
+ ret = LZO_E_OK;
+ } else {
+ ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
uncmem, &clen);
+ }

if (is_partial_io(bvec)) {
memcpy(user_mem + bvec->bv_offset, uncmem + offset,
@@ -342,8 +347,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
goto out;
}

- if (unlikely(clen > max_zpage_size))
+ if (unlikely(clen > max_zpage_size)) {
zram_stat_inc(&zram->stats.bad_compress);
+ src = uncmem;
+ clen = PAGE_SIZE;
+ }

handle = zs_malloc(zram->mem_pool, clen);
if (!handle) {
--
1.7.9.5


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