f2fs: extend stat_lock to avoid potential race in statfs

There are multiple calculations and reads of fields of sbi that should
be protected by stat_lock. As stat_lock is not used to read these
values in statfs, this can lead to inconsistent results.
Extend the locking to prevent this issue.
Commit c9c8ed50d94c ("f2fs: fix to avoid potential race on
sbi->unusable_block_count access/update")
already added the use of sbi->stat_lock in statfs in
order to make the calculation of multiple, different fields atomic so
that results are consistent. This is similar to that patch regarding the
change in statfs.

Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 4368f90571bd6194a992ba0bed1b7a109dcee597..cb50f8b2e41ad158c7ca0535da400c2e45ea7060 100644 (file)
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1707,18 +1707,23 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
        block_t total_count, user_block_count, start_count;
        u64 avail_node_count;
+       unsigned int total_valid_node_count;
 
        total_count = le64_to_cpu(sbi->raw_super->block_count);
-       user_block_count = sbi->user_block_count;
        start_count = le32_to_cpu(sbi->raw_super->segment0_blkaddr);
        buf->f_type = F2FS_SUPER_MAGIC;
        buf->f_bsize = sbi->blocksize;
 
        buf->f_blocks = total_count - start_count;
+
+       spin_lock(&sbi->stat_lock);
+
+       user_block_count = sbi->user_block_count;
+       total_valid_node_count = valid_node_count(sbi);
+       avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
        buf->f_bfree = user_block_count - valid_user_blocks(sbi) -
                                                sbi->current_reserved_blocks;
 
-       spin_lock(&sbi->stat_lock);
        if (unlikely(buf->f_bfree <= sbi->unusable_block_count))
                buf->f_bfree = 0;
        else
@@ -1731,14 +1736,12 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
        else
                buf->f_bavail = 0;
 
-       avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
-
        if (avail_node_count > user_block_count) {
                buf->f_files = user_block_count;
                buf->f_ffree = buf->f_bavail;
        } else {
                buf->f_files = avail_node_count;
-               buf->f_ffree = min(avail_node_count - valid_node_count(sbi),
+               buf->f_ffree = min(avail_node_count - total_valid_node_count,
                                        buf->f_bavail);
        }