Hi Jaegeuk,
On Sun, Mar 08, 2015 at 09:18:47PM -0700, Jaegeuk Kim wrote:
>Hi Wanpeng,
>
>On Mon, Mar 09, 2015 at 11:00:54AM +0800, Wanpeng Li wrote:
>> The blocks of nat pages to be scanned will be readahead when build free
>> nids. The start blkno will be adjusted to 0 when the intended range over
>> max_nids, then function ra_meta_pages readahead the right blkno, however,
>> function get_current_nat_page which is called in build_free_nids still
>> get the meta pages w/ stale blkno, this patch fix it by adjusting the nid
>> and the blkno which will be readahead in avdance in order to readahead and
>> get the right meta pages.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
>> ---
>> fs/f2fs/checkpoint.c | 3 ---
>> fs/f2fs/node.c | 9 ++++++++-
>> 2 files changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index 53bc328..aedb441 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -129,9 +129,6 @@ int ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages, int type
>>
>> switch (type) {
>> case META_NAT:
>> - if (unlikely(blkno >=
>> - NAT_BLOCK_OFFSET(NM_I(sbi)->max_nid)))
>> - blkno = 0;
>> /* get nat block addr */
>> fio.blk_addr = current_nat_addr(sbi,
>> blkno * NAT_ENTRY_PER_BLOCK);
>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>> index 1a7e925..8751375 100644
>> --- a/fs/f2fs/node.c
>> +++ b/fs/f2fs/node.c
>> @@ -1509,13 +1509,20 @@ static void build_free_nids(struct f2fs_sb_info *sbi)
>> struct f2fs_summary_block *sum = curseg->sum_blk;
>> int i = 0;
>> nid_t nid = nm_i->next_scan_nid;
>> + block_t blkno = NAT_BLOCK_OFFSET(nid);
>>
>> /* Enough entries */
>> if (nm_i->fcnt > NAT_ENTRY_PER_BLOCK)
>> return;
>>
>> + if (unlikely(blkno >=
>> + NAT_BLOCK_OFFSET(NM_I(sbi)->max_nid))) {
>> + blkno = 0;
>> + nid = 0;
>> + }
>
>The assumption here is that the nid does not exceeed max_nid, since the
>previous call already set next_scan_nid to 0, if it exceeds max_nid.
>So, we don't need to do like this.
So get_current_nat_page in while(1) still get the wrong meta page for
one time, right? The nid will be set to 0 in the second round.
Regards,
Wanpeng Li
>
>BTW, even if ra_meta_pages doesn't get the below condition,
> if (unlikely(blkno >=
> NAT_BLOCK_OFFSET(NM_I(sbi)->max_nid)))
> blkno = 0;
>IMO, it is still worth to remain that to avoid any bugs due to further code
>changes. It makes sense that unlikely was used for this too.
>
>Thanks,
>
>> +
>> /* readahead nat pages to be scanned */
>> - ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), FREE_NID_PAGES, META_NAT);
>> + ra_meta_pages(sbi, blkno, FREE_NID_PAGES, META_NAT);
>>
>> while (1) {
>> struct page *page = get_current_nat_page(sbi, nid);
>> --
>> 1.9.1
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