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
fs_lock
allocation(GFP_KERNEL)
reclaim
pageout
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.
Cc: sta...@vger.kernel.org
Cc: Jerome Marchand <jmarc...@redhat.com>
Acked-by: Nitin Gupta <ngu...@vflare.org>
[ penb...@kernel.org: don't use GFP_ATOMIC ]
Signed-off-by: Pekka Enberg <penb...@kernel.org>
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
drivers/staging/zram/zram_drv.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 77a3f0d..5ff8749 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -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);
- else
+ 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;
--
1.7.9.5
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