f2fs: avoid data race when deciding checkpoin in f2fs_sync_file
When fs utilization is almost full, f2fs_sync_file should do checkpoint if
there is not enough space for roll-forward later. (i.e. space_for_roll_forward)
So, currently we have no lock for sbi->alloc_valid_block_count, resulting in
race condition.
In rare case, we can get -ENOSPC when doing roll-forward which triggers
if (is_valid_blkaddr(sbi, dest, META_POR)) {
if (src == NULL_ADDR) {
err = reserve_new_block(&dn);
f2fs_bug_on(sbi, err);
...
}
...
}
in do_recover_data.
So, this patch avoids that situation in advance.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 399de97..1a2d8a8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1165,24 +1165,33 @@
static inline bool inc_valid_block_count(struct f2fs_sb_info *sbi,
struct inode *inode, blkcnt_t *count)
{
+ blkcnt_t diff;
+
#ifdef CONFIG_F2FS_FAULT_INJECTION
if (time_to_inject(FAULT_BLOCK))
return false;
#endif
+ /*
+ * let's increase this in prior to actual block count change in order
+ * for f2fs_sync_file to avoid data races when deciding checkpoint.
+ */
+ percpu_counter_add(&sbi->alloc_valid_block_count, (*count));
+
spin_lock(&sbi->stat_lock);
sbi->total_valid_block_count += (block_t)(*count);
if (unlikely(sbi->total_valid_block_count > sbi->user_block_count)) {
- *count -= sbi->total_valid_block_count - sbi->user_block_count;
+ diff = sbi->total_valid_block_count - sbi->user_block_count;
+ *count -= diff;
sbi->total_valid_block_count = sbi->user_block_count;
if (!*count) {
spin_unlock(&sbi->stat_lock);
+ percpu_counter_sub(&sbi->alloc_valid_block_count, diff);
return false;
}
}
spin_unlock(&sbi->stat_lock);
f2fs_i_blocks_write(inode, *count, true);
- percpu_counter_add(&sbi->alloc_valid_block_count, (*count));
return true;
}