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SubjectRe: [f2fs-dev] [PATCH RESEND v2] f2fs: fix concurrent problem for updating free bitmap
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On 2017/11/21 16:19, LiFan wrote:
> alloc_nid_failed and scan_nat_page can be called at the same time,
> and we haven't protected add_free_nid and update_free_nid_bitmap
> with the same nid_list_lock. That could lead to
>
> Thread A Thread B
> - __build_free_nids
> - scan_nat_page
> - add_free_nid
> - alloc_nid_failed
> - update_free_nid_bitmap
> - update_free_nid_bitmap
>
> scan_nat_page will clear the free bitmap since the nid is PREALLOC_NID,
> but alloc_nid_failed needs to set the free bitmap. This results in
> free nid with free bitmap cleared.
> This patch update the bitmap under the same nid_list_lock in add_free_nid.
> And use __GFP_NOFAIL to make sure to update status of free nid correctly.
>
> Signed-off-by: Fan li <fanofcode.li@samsung.com>
> ---
> fs/f2fs/node.c | 84 ++++++++++++++++++++++++++++++----------------------------
> 1 file changed, 43 insertions(+), 41 deletions(-)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index b965a53..dd299c5 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1811,8 +1811,33 @@ static void __move_free_nid(struct f2fs_sb_info *sbi, struct free_nid *i,
> }
> }
>
> +static void update_free_nid_bitmap(struct f2fs_sb_info *sbi, nid_t nid,
> + bool set, bool build)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> + unsigned int nat_ofs = NAT_BLOCK_OFFSET(nid);
> + unsigned int nid_ofs = nid - START_NID(nid);
> +
> + if (!test_bit_le(nat_ofs, nm_i->nat_block_bitmap))
> + return;
> +
> + if (set) {
> + if (test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
> + return;
> + __set_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> + nm_i->free_nid_count[nat_ofs]++;
> + } else {
> + if (!test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
> + return;
> + __clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> + if (!build)
> + nm_i->free_nid_count[nat_ofs]--;
> + }
> +}
> +
> /* return if the nid is recognized as free */
> -static bool add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
> +static bool add_free_nid(struct f2fs_sb_info *sbi,
> + nid_t nid, bool build, bool update)
> {
> struct f2fs_nm_info *nm_i = NM_I(sbi);
> struct free_nid *i, *e;
> @@ -1828,7 +1853,7 @@ static bool add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
> i->nid = nid;
> i->state = FREE_NID;
>
> - if (radix_tree_preload(GFP_NOFS))
> + if (radix_tree_preload(GFP_NOFS | __GFP_NOFAIL))
> goto err;

We will never fail if we call radix_tree_preload with __GFP_NOFAIL, so
we don't need to check return value here.

BTW, I can not apply this patch, could you rebase this patch on last
dev-test branch?

Thanks,

>
> spin_lock(&nm_i->nid_list_lock);
> @@ -1870,6 +1895,11 @@ static bool add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
> ret = true;
> err = __insert_free_nid(sbi, i, FREE_NID);
> err_out:
> + if (update) {
> + update_free_nid_bitmap(sbi, nid, ret, build);
> + if (!build)
> + nm_i->available_nids++;
> + }
> spin_unlock(&nm_i->nid_list_lock);
> radix_tree_preload_end();
> err:
> @@ -1896,30 +1926,6 @@ static void remove_free_nid(struct f2fs_sb_info *sbi, nid_t nid)
> kmem_cache_free(free_nid_slab, i);
> }
>
> -static void update_free_nid_bitmap(struct f2fs_sb_info *sbi, nid_t nid,
> - bool set, bool build)
> -{
> - struct f2fs_nm_info *nm_i = NM_I(sbi);
> - unsigned int nat_ofs = NAT_BLOCK_OFFSET(nid);
> - unsigned int nid_ofs = nid - START_NID(nid);
> -
> - if (!test_bit_le(nat_ofs, nm_i->nat_block_bitmap))
> - return;
> -
> - if (set) {
> - if (test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
> - return;
> - __set_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> - nm_i->free_nid_count[nat_ofs]++;
> - } else {
> - if (!test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
> - return;
> - __clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> - if (!build)
> - nm_i->free_nid_count[nat_ofs]--;
> - }
> -}
> -
> static void scan_nat_page(struct f2fs_sb_info *sbi,
> struct page *nat_page, nid_t start_nid)
> {
> @@ -1937,18 +1943,18 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
> i = start_nid % NAT_ENTRY_PER_BLOCK;
>
> for (; i < NAT_ENTRY_PER_BLOCK; i++, start_nid++) {
> - bool freed = false;
> -
> if (unlikely(start_nid >= nm_i->max_nid))
> break;
>
> blk_addr = le32_to_cpu(nat_blk->entries[i].block_addr);
> f2fs_bug_on(sbi, blk_addr == NEW_ADDR);
> - if (blk_addr == NULL_ADDR)
> - freed = add_free_nid(sbi, start_nid, true);
> - spin_lock(&NM_I(sbi)->nid_list_lock);
> - update_free_nid_bitmap(sbi, start_nid, freed, true);
> - spin_unlock(&NM_I(sbi)->nid_list_lock);
> + if (blk_addr == NULL_ADDR) {
> + add_free_nid(sbi, start_nid, true, true);
> + } else {
> + spin_lock(&NM_I(sbi)->nid_list_lock);
> + update_free_nid_bitmap(sbi, start_nid, false, true);
> + spin_unlock(&NM_I(sbi)->nid_list_lock);
> + }
> }
> }
>
> @@ -1974,7 +1980,7 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
> break;
>
> nid = i * NAT_ENTRY_PER_BLOCK + idx;
> - add_free_nid(sbi, nid, true);
> + add_free_nid(sbi, nid, true, false);
>
> if (nm_i->nid_cnt[FREE_NID] >= MAX_FREE_NIDS)
> goto out;
> @@ -1988,7 +1994,7 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
> addr = le32_to_cpu(nat_in_journal(journal, i).block_addr);
> nid = le32_to_cpu(nid_in_journal(journal, i));
> if (addr == NULL_ADDR)
> - add_free_nid(sbi, nid, true);
> + add_free_nid(sbi, nid, true, false);
> else
> remove_free_nid(sbi, nid);
> }
> @@ -2053,7 +2059,7 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
> addr = le32_to_cpu(nat_in_journal(journal, i).block_addr);
> nid = le32_to_cpu(nid_in_journal(journal, i));
> if (addr == NULL_ADDR)
> - add_free_nid(sbi, nid, true);
> + add_free_nid(sbi, nid, true, false);
> else
> remove_free_nid(sbi, nid);
> }
> @@ -2499,11 +2505,7 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
> nat_reset_flag(ne);
> __clear_nat_cache_dirty(NM_I(sbi), set, ne);
> if (nat_get_blkaddr(ne) == NULL_ADDR) {
> - add_free_nid(sbi, nid, false);
> - spin_lock(&NM_I(sbi)->nid_list_lock);
> - NM_I(sbi)->available_nids++;
> - update_free_nid_bitmap(sbi, nid, true, false);
> - spin_unlock(&NM_I(sbi)->nid_list_lock);
> + add_free_nid(sbi, nid, false, true);
> } else {
> spin_lock(&NM_I(sbi)->nid_list_lock);
> update_free_nid_bitmap(sbi, nid, false, false);
>

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