[PATCH v3] f2fs: fix out-of-free problem caused by atomic write

From: Yunlong Song
Date: Sun Nov 05 2017 - 21:08:43 EST


f2fs_balance_fs only actives once in the commit_inmem_pages, but there
are more than one page to commit, so all the other pages will miss the
check. This will lead to out-of-free problem when commit a very large
file. However, we cannot do f2fs_balance_fs for each inmem page, since
this will break atomicity. As a result, we should collect prefree
segments if needed.

Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
---
fs/f2fs/f2fs.h | 1 +
fs/f2fs/segment.c | 24 +++++++++++++++++++++++-
2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 13a96b8..04ce48f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -610,6 +610,7 @@ struct f2fs_inode_info {
struct list_head inmem_pages; /* inmemory pages managed by f2fs */
struct task_struct *inmem_task; /* store inmemory task */
struct mutex inmem_lock; /* lock for inmemory pages */
+ unsigned long inmem_blocks; /* inmemory blocks */
struct extent_tree *extent_tree; /* cached extent_tree entry */
struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
struct rw_semaphore i_mmap_sem;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 46dfbca..b87ede4 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -210,6 +210,7 @@ void register_inmem_page(struct inode *inode, struct page *page)
list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
+ fi->inmem_blocks++;
mutex_unlock(&fi->inmem_lock);

trace_f2fs_register_inmem_page(page, INMEM);
@@ -221,6 +222,7 @@ static int __revoke_inmem_pages(struct inode *inode,
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct inmem_pages *cur, *tmp;
int err = 0;
+ struct f2fs_inode_info *fi = F2FS_I(inode);

list_for_each_entry_safe(cur, tmp, head, list) {
struct page *page = cur->page;
@@ -263,6 +265,7 @@ static int __revoke_inmem_pages(struct inode *inode,
list_del(&cur->list);
kmem_cache_free(inmem_entry_slab, cur);
dec_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
+ fi->inmem_blocks--;
}
return err;
}
@@ -302,6 +305,10 @@ void drop_inmem_pages(struct inode *inode)
if (!list_empty(&fi->inmem_ilist))
list_del_init(&fi->inmem_ilist);
spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+ if (fi->inmem_blocks) {
+ f2fs_bug_on(sbi, 1);
+ fi->inmem_blocks = 0;
+ }
mutex_unlock(&fi->inmem_lock);

clear_inode_flag(inode, FI_ATOMIC_FILE);
@@ -326,6 +333,7 @@ void drop_inmem_page(struct inode *inode, struct page *page)

f2fs_bug_on(sbi, !cur || cur->page != page);
list_del(&cur->list);
+ fi->inmem_blocks--;
mutex_unlock(&fi->inmem_lock);

dec_page_count(sbi, F2FS_INMEM_PAGES);
@@ -410,6 +418,16 @@ int commit_inmem_pages(struct inode *inode)

INIT_LIST_HEAD(&revoke_list);
f2fs_balance_fs(sbi, true);
+ if (prefree_segments(sbi)
+ && has_not_enough_free_secs(sbi, 0,
+ fi->inmem_blocks / BLKS_PER_SEC(sbi))) {
+ struct cp_control cpc;
+
+ cpc.reason = __get_cp_reason(sbi);
+ err = write_checkpoint(sbi, &cpc);
+ if (err)
+ goto drop;
+ }
f2fs_lock_op(sbi);

set_inode_flag(inode, FI_ATOMIC_COMMIT);
@@ -429,7 +447,7 @@ int commit_inmem_pages(struct inode *inode)
ret = __revoke_inmem_pages(inode, &revoke_list, false, true);
if (ret)
err = ret;
-
+drop:
/* drop all uncommitted pages */
__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
}
@@ -437,6 +455,10 @@ int commit_inmem_pages(struct inode *inode)
if (!list_empty(&fi->inmem_ilist))
list_del_init(&fi->inmem_ilist);
spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+ if (fi->inmem_blocks) {
+ f2fs_bug_on(sbi, 1);
+ fi->inmem_blocks = 0;
+ }
mutex_unlock(&fi->inmem_lock);

clear_inode_flag(inode, FI_ATOMIC_COMMIT);
--
1.8.5.2