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Subject[PATCH] f2fs: avoid migratepage for atomic written page
Date
In order to avoid lock contention for atomic written pages, we'd better give
EAGAIN in f2fs_migrate_page. We expect it will be released soon as transaction
commits.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/data.c | 35 ++++++++++-------------------------
1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index d58b81213a86..1458e3a6d630 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2197,41 +2197,26 @@ static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
int f2fs_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
- int rc, extra_count;
- struct f2fs_inode_info *fi = F2FS_I(mapping->host);
- bool atomic_written = IS_ATOMIC_WRITTEN_PAGE(page);
+ int rc;

- BUG_ON(PageWriteback(page));
-
- /* migrating an atomic written page is safe with the inmem_lock hold */
- if (atomic_written && !mutex_trylock(&fi->inmem_lock))
+ /*
+ * We'd better return EAGAIN for atomic pages, which will be committed
+ * sooner or later. Don't botter transactions with inmem_lock.
+ */
+ if (IS_ATOMIC_WRITTEN_PAGE(page))
return -EAGAIN;

+ BUG_ON(PageWriteback(page)); /* Writeback must be complete */
+
/*
* A reference is expected if PagePrivate set when move mapping,
* however F2FS breaks this for maintaining dirty page counts when
* truncating pages. So here adjusting the 'extra_count' make it work.
*/
- extra_count = (atomic_written ? 1 : 0) - page_has_private(page);
rc = migrate_page_move_mapping(mapping, newpage,
- page, NULL, mode, extra_count);
- if (rc != MIGRATEPAGE_SUCCESS) {
- if (atomic_written)
- mutex_unlock(&fi->inmem_lock);
+ page, NULL, mode, (page_has_private(page) ? -1 : 0));
+ if (rc != MIGRATEPAGE_SUCCESS)
return rc;
- }
-
- if (atomic_written) {
- struct inmem_pages *cur;
- list_for_each_entry(cur, &fi->inmem_pages, list)
- if (cur->page == page) {
- cur->page = newpage;
- break;
- }
- mutex_unlock(&fi->inmem_lock);
- put_page(page);
- get_page(newpage);
- }

if (PagePrivate(page))
SetPagePrivate(newpage);
--
2.13.0.rc1.294.g07d810a77f-goog
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