On Thu, Dec 24, 2020 at 1:16 PM Tian Tao <tiantao6@xxxxxxxxxxxxx> wrote:
add a flag to zpool, named is "can_sleep_mapped", and have it set true
for zbud/z3fold, set false for zsmalloc. Then zswap could go the current
path if the flag is true; and if it's false, copy data from src to a
temporary buffer, then unmap the handle, take the mutex, process the
buffer instead of src to avoid sleeping function called from atomic
context.
Signed-off-by: Tian Tao <tiantao6@xxxxxxxxxxxxx>
---
include/linux/zpool.h | 2 ++
mm/z3fold.c | 1 +
mm/zbud.c | 1 +
mm/zpool.c | 13 +++++++++++++
mm/zsmalloc.c | 1 +
mm/zswap.c | 23 +++++++++++++++++++++--
6 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/include/linux/zpool.h b/include/linux/zpool.h
index 51bf430..a354f4fe 100644
--- a/include/linux/zpool.h
+++ b/include/linux/zpool.h
@@ -82,6 +82,7 @@ u64 zpool_get_total_size(struct zpool *pool);
*/
struct zpool_driver {
char *type;
+ bool sleep_mapped;
Could you please add this somewhat further down, close to map / unmap
callbacks, and add a description of the field above, too?
struct module *owner;
atomic_t refcount;
struct list_head list;
@@ -112,5 +113,6 @@ void zpool_register_driver(struct zpool_driver *driver);
int zpool_unregister_driver(struct zpool_driver *driver);
bool zpool_evictable(struct zpool *pool);
+bool zpool_can_sleep_mapped(struct zpool *pool);
#endif
diff --git a/mm/z3fold.c b/mm/z3fold.c
index dacb0d7..234b46f 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1778,6 +1778,7 @@ static u64 z3fold_zpool_total_size(void *pool)
static struct zpool_driver z3fold_zpool_driver = {
.type = "z3fold",
+ .sleep_mapped = true,
.owner = THIS_MODULE,
.create = z3fold_zpool_create,
.destroy = z3fold_zpool_destroy,
diff --git a/mm/zbud.c b/mm/zbud.c
index c49966e..7ec5f27 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -203,6 +203,7 @@ static u64 zbud_zpool_total_size(void *pool)
static struct zpool_driver zbud_zpool_driver = {
.type = "zbud",
+ .sleep_mapped = true,
.owner = THIS_MODULE,
.create = zbud_zpool_create,
.destroy = zbud_zpool_destroy,
diff --git a/mm/zpool.c b/mm/zpool.c
index 3744a2d..5ed7120 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -23,6 +23,7 @@ struct zpool {
void *pool;
const struct zpool_ops *ops;
bool evictable;
+ bool can_sleep_mapped;
struct list_head list;
};
@@ -183,6 +184,7 @@ struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
zpool->pool = driver->create(name, gfp, ops, zpool);
zpool->ops = ops;
zpool->evictable = driver->shrink && ops && ops->evict;
+ zpool->can_sleep_mapped = driver->sleep_mapped;
if (!zpool->pool) {
pr_err("couldn't create %s pool\n", type);
@@ -393,6 +395,17 @@ bool zpool_evictable(struct zpool *zpool)
return zpool->evictable;
}
+/**
+ * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
+ * @zpool: The zpool to test
+ *
+ * Returns: true if zpool can sleep; false otherwise.
+ */
+bool zpool_can_sleep_mapped(struct zpool *zpool)
+{
+ return zpool->can_sleep_mapped;
+}
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dan Streetman <ddstreet@xxxxxxxx>");
MODULE_DESCRIPTION("Common API for compressed memory storage");
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7289f50..a991d3c 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -440,6 +440,7 @@ static u64 zs_zpool_total_size(void *pool)
static struct zpool_driver zs_zpool_driver = {
.type = "zsmalloc",
+ .sleep_mapped = false,
You don't have to add this, it will be false if not explicitly specified.
.owner = THIS_MODULE,
.create = zs_zpool_create,
.destroy = zs_zpool_destroy,
diff --git a/mm/zswap.c b/mm/zswap.c
index 182f6ad..51b033a 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1235,7 +1235,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
struct zswap_entry *entry;
struct scatterlist input, output;
struct crypto_acomp_ctx *acomp_ctx;
- u8 *src, *dst;
+ u8 *src, *dst, *tmp;
unsigned int dlen;
int ret;
@@ -1256,12 +1256,27 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
goto freeentry;
}
+ if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
+
+ tmp = kzalloc(entry->length, GFP_KERNEL);
Do we really need kzalloc here? the buffer will be written to in a few
moments anyway.
Also, we allocate a small buffer for a short while, and this is likely
to be a performance critical path, so GFP_ATOMIC looks more
appropriate.
+ if (!tmp)
+ return -ENOMEM;
You can't just return here, you need to call zswap_entry_put() first.
Since this is obviously not the final version of your patch, could you
please split it in 2 the next time? I'd prefer setting flags to
specific backends in a separate patch.
