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f2fs: avoid data race when deciding checkpoin in f2fs_sync_file

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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>
This commit is contained in:
Jaegeuk Kim 2016-07-19 19:20:11 -07:00
parent 4dd6f977fc
commit dd11a5df52
1 changed files with 11 additions and 2 deletions
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13
fs/f2fs/f2fs.h
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@ -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;
}