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Subject[f2fs-dev] [PATCH RESEND] f2fs: fix concurrent problem for updating free bitmap
Date
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.

Signed-off-by: Fan li <fanofcode.li@samsung.com>
---
fs/f2fs/node.c | 82 ++++++++++++++++++++++++++++++----------------------------
1 file changed, 42 insertions(+), 40 deletions(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index b965a53..0a217d2 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;
@@ -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);
--
2.7.4

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