Commit 7e5a5104 authored by Minchan Kim's avatar Minchan Kim Committed by Greg Kroah-Hartman

zram: Fix deadlock bug in partial read/write

Now zram allocates new page with GFP_KERNEL in zram I/O path
if IO is partial. Unfortunately, It may cause deadlock with
reclaim path like below.

write_page from fs
				write_page from fs
				fs_lock <-- deadlock

This patch fixes it by using GFP_NOIO.  In read path, we
reorganize code flow so that kmap_atomic is called after the
GFP_NOIO allocation.

Acked-by: default avatarJerome Marchand <>
Acked-by: default avatarNitin Gupta <>
[ don't use GFP_ATOMIC ]
Signed-off-by: default avatarPekka Enberg <>
Signed-off-by: default avatarMinchan Kim <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 7f70410f
......@@ -217,11 +217,12 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
return 0;
user_mem = kmap_atomic(page);
if (is_partial_io(bvec))
/* Use a temporary buffer to decompress the page */
uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
user_mem = kmap_atomic(page);
if (!is_partial_io(bvec))
uncmem = user_mem;
if (!uncmem) {
......@@ -268,7 +269,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
* This is a partial IO. We need to read the full page
* before to write the changes.
uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
if (!uncmem) {
pr_info("Error allocating temp memory!\n");
ret = -ENOMEM;
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