f2fs: flush dirty nat entries when exceeding threshold
When testing f2fs with xfstest, generic/251 is stuck for long time, the case uses below serials to obtain fresh released space in device, in order to prepare for following fstrim test. 1. rm -rf /mnt/dir 2. mkdir /mnt/dir/ 3. cp -axT `pwd`/ /mnt/dir/ 4. goto 1 During preparing step, all nat entries will be cached in nat cache, most of them are dirty entries with invalid blkaddr, which means nodes related to these entries have been truncated, and they could be reused after the dirty entries been checkpointed. However, there was no checkpoint been triggered, so nid allocators (e.g. mkdir, creat) will run into long journey of iterating all NAT pages, looking for free nids in alloc_nid->build_free_nids. Here, in f2fs_balance_fs_bg we give another chance to do checkpoint to flush nat entries for reusing them in free nid cache when dirty entry count exceeds 10% of max count. Signed-off-by: NChao Yu <chao2.yu@samsung.com> Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>
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