From dd11a5df5219b4d3c4d3f38b9cae48c3518d3152 Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim Date: Tue, 19 Jul 2016 19:20:11 -0700 Subject: [PATCH] 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 --- fs/f2fs/f2fs.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 7a57279b2c54..30981094dff8 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -1147,24 +1147,33 @@ static inline void f2fs_i_blocks_write(struct inode *, blkcnt_t, bool); 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; } -- 2.34.1