f2fs: avoid deadlock during evict after f2fs_gc
o Deadlock case #1
Thread 1:
- writeback_sb_inodes
- do_writepages
- f2fs_write_data_pages
- write_cache_pages
- f2fs_write_data_page
- f2fs_balance_fs
- wait mutex_lock(gc_mutex)
Thread 2:
- f2fs_balance_fs
- mutex_lock(gc_mutex)
- f2fs_gc
- f2fs_iget
- wait iget_locked(inode->i_lock)
Thread 3:
- do_unlinkat
- iput
- lock(inode->i_lock)
- evict
- inode_wait_for_writeback
o Deadlock case #2
Thread 1:
- __writeback_single_inode
: set I_SYNC
- do_writepages
- f2fs_write_data_page
- f2fs_balance_fs
- f2fs_gc
- iput
- evict
- inode_wait_for_writeback(I_SYNC)
In order to avoid this, even though iput is called with the zero-reference
count, we need to stop the eviction procedure if the inode is on writeback.
So this patch links f2fs_drop_inode which checks the I_SYNC flag.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 2db9380..61b4454 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -577,6 +577,7 @@
{
struct inode *inode = mapping->host;
struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
+ bool locked = false;
int ret;
long excess_nrtw = 0, desired_nrtw;
@@ -590,10 +591,12 @@
wbc->nr_to_write = desired_nrtw;
}
- if (!S_ISDIR(inode->i_mode))
+ if (!S_ISDIR(inode->i_mode)) {
mutex_lock(&sbi->writepages);
+ locked = true;
+ }
ret = write_cache_pages(mapping, wbc, __f2fs_writepage, mapping);
- if (!S_ISDIR(inode->i_mode))
+ if (locked)
mutex_unlock(&sbi->writepages);
f2fs_submit_bio(sbi, DATA, (wbc->sync_mode == WB_SYNC_ALL));