Pages containing buffer_heads that are in the buffer_head LRU cache
will be pinned and thus cannot be migrated. Correspondingly,
invalidate the BH LRU before a migration starts and stop any
buffer_head from being cached in the LRU, until migration has
finished.
Signed-off-by: Chris Goldsworthy <cgold...@codeaurora.org>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Matthew Wilcox <wi...@infradead.org>
---
fs/buffer.c | 6 ++++++
include/linux/buffer_head.h | 3 +++
include/linux/migrate.h | 2 ++
mm/migrate.c | 18 ++++++++++++++++++
mm/page_alloc.c | 3 +++
mm/swap.c | 3 +++
6 files changed, 35 insertions(+)
diff --git a/fs/buffer.c b/fs/buffer.c
index 96c7604..39ec4ec 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1289,6 +1289,8 @@ static inline void check_irqs_on(void)
#endif
}
+bool bh_migration_done = true;
+
/*
* Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
* inserted at the front, and the buffer_head at the back if any is evicted.
@@ -1303,6 +1305,9 @@ static void bh_lru_install(struct buffer_head *bh)
check_irqs_on();
bh_lru_lock();
+ if (!bh_migration_done)
+ goto out;
+
b = this_cpu_ptr(&bh_lrus);
for (i = 0; i < BH_LRU_SIZE; i++) {
swap(evictee, b->bhs[i]);
@@ -1313,6 +1318,7 @@ static void bh_lru_install(struct buffer_head *bh)
}
get_bh(bh);
+out:
bh_lru_unlock();
brelse(evictee);
}
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 6b47f94..ae4eb6d 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -193,6 +193,9 @@ void __breadahead_gfp(struct block_device *, sector_t
block, unsigned int size,
gfp_t gfp);
struct buffer_head *__bread_gfp(struct block_device *,
sector_t block, unsigned size, gfp_t gfp);
+
+extern bool bh_migration_done;
+
void invalidate_bh_lrus(void);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 3a38963..9e4a2dc 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -46,6 +46,7 @@ extern int isolate_movable_page(struct page *page,
isolate_mode_t mode);
extern void putback_movable_page(struct page *page);
extern void migrate_prep(void);
+extern void migrate_finish(void);
extern void migrate_prep_local(void);
extern void migrate_page_states(struct page *newpage, struct page *page);
extern void migrate_page_copy(struct page *newpage, struct page *page);
@@ -67,6 +68,7 @@ static inline int isolate_movable_page(struct page *page,
isolate_mode_t mode)
{ return -EBUSY; }
static inline int migrate_prep(void) { return -ENOSYS; }
+static inline int migrate_finish(void) { return -ENOSYS; }
static inline int migrate_prep_local(void) { return -ENOSYS; }
static inline void migrate_page_states(struct page *newpage, struct page *page)
diff --git a/mm/migrate.c b/mm/migrate.c
index a69da8a..08c981d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -64,6 +64,19 @@
*/
void migrate_prep(void)
{
+ bh_migration_done = false;
+
+ /*
+ * This barrier ensures that callers of bh_lru_install() between
+ * the barrier and the call to invalidate_bh_lrus() read
+ * bh_migration_done() as false.
+ */
+ /*
+ * TODO: Remove me? lru_add_drain_all() already has an smp_mb(),
+ * but it would be good to ensure that the barrier isn't forgotten.
+ */
+ smp_mb();
+
/*
* Clear the LRU lists so pages can be isolated.
* Note that pages may be moved off the LRU after we have
@@ -73,6 +86,11 @@ void migrate_prep(void)
lru_add_drain_all();
}
+void migrate_finish(void)
+{
+ bh_migration_done = true;
+}
+
/* Do the necessary work of migrate_prep but not if it involves other CPUs */
void migrate_prep_local(void)
{
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6446778..e4cb959 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8493,6 +8493,9 @@ static int __alloc_contig_migrate_range(struct
compact_control *cc,
ret = migrate_pages(&cc->migratepages, alloc_migration_target,
NULL, (unsigned long)&mtc, cc->mode,
MR_CONTIG_RANGE);
}
+
+ migrate_finish();
+
if (ret < 0) {
putback_movable_pages(&cc->migratepages);
return ret;
diff --git a/mm/swap.c b/mm/swap.c
index 31b844d..97efc49 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -36,6 +36,7 @@
#include <linux/hugetlb.h>
#include <linux/page_idle.h>
#include <linux/local_lock.h>
+#include <linux/buffer_head.h>
#include "internal.h"
@@ -759,6 +760,8 @@ void lru_add_drain_all(void)
if (WARN_ON(!mm_percpu_wq))
return;
+ invalidate_bh_lrus();
+
/*
* Guarantee pagevec counter stores visible by this CPU are visible to
* other CPUs before loading the current drain generation.
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
