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bcachefs: Move snapshot table size to struct snapshot_table

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We need to add bounds checking for snapshot table accesses - it turns
out there are cases where we do need to use the snapshots table before
fsck checks have completed (and indeed, fsck may not have been run).

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-03-21 20:16:23 -04:00
parent aa6e130e3c
commit 63332394c7
4 changed files with 21 additions and 13 deletions
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1
fs/bcachefs/bcachefs.h
View File

@ -810,7 +810,6 @@ struct bch_fs {
/* snapshot.c: */
struct snapshot_table __rcu *snapshots;
size_t snapshot_table_size;
struct mutex snapshot_table_lock;
struct rw_semaphore snapshot_create_lock;

25
fs/bcachefs/snapshot.c
View File

@ -151,36 +151,39 @@ out:
static noinline struct snapshot_t *__snapshot_t_mut(struct bch_fs *c, u32 id)
{
size_t idx = U32_MAX - id;
size_t new_size;
struct snapshot_table *new, *old;
new_size = max(16UL, roundup_pow_of_two(idx + 1));
size_t new_bytes = kmalloc_size_roundup(struct_size(new, s, idx + 1));
size_t new_size = (new_bytes - sizeof(*new)) / sizeof(new->s[0]);
new = kvzalloc(struct_size(new, s, new_size), GFP_KERNEL);
new = kvzalloc(new_bytes, GFP_KERNEL);
if (!new)
return NULL;
new->nr = new_size;
old = rcu_dereference_protected(c->snapshots, true);
if (old)
memcpy(new->s,
rcu_dereference_protected(c->snapshots, true)->s,
sizeof(new->s[0]) * c->snapshot_table_size);
memcpy(new->s, old->s, sizeof(old->s[0]) * old->nr);
rcu_assign_pointer(c->snapshots, new);
c->snapshot_table_size = new_size;
kvfree_rcu_mightsleep(old);
kvfree_rcu(old, rcu);
return &rcu_dereference_protected(c->snapshots, true)->s[idx];
return &rcu_dereference_protected(c->snapshots,
lockdep_is_held(&c->snapshot_table_lock))->s[idx];
}
static inline struct snapshot_t *snapshot_t_mut(struct bch_fs *c, u32 id)
{
size_t idx = U32_MAX - id;
struct snapshot_table *table =
rcu_dereference_protected(c->snapshots,
lockdep_is_held(&c->snapshot_table_lock));
lockdep_assert_held(&c->snapshot_table_lock);
if (likely(idx < c->snapshot_table_size))
return &rcu_dereference_protected(c->snapshots, true)->s[idx];
if (likely(table && idx < table->nr))
return &table->s[idx];
return __snapshot_t_mut(c, id);
}

6
fs/bcachefs/snapshot.h
View File

@ -33,7 +33,11 @@ int bch2_mark_snapshot(struct btree_trans *, enum btree_id, unsigned,
static inline struct snapshot_t *__snapshot_t(struct snapshot_table *t, u32 id)
{
return &t->s[U32_MAX - id];
u32 idx = U32_MAX - id;
return likely(t && idx < t->nr)
? &t->s[idx]
: NULL;
}
static inline const struct snapshot_t *snapshot_t(struct bch_fs *c, u32 id)

2
fs/bcachefs/subvolume_types.h
View File

@ -20,6 +20,8 @@ struct snapshot_t {
};
struct snapshot_table {
struct rcu_head rcu;
size_t nr;
#ifndef RUST_BINDGEN
DECLARE_FLEX_ARRAY(struct snapshot_t, s);
#else