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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>