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.
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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