@@ -1979,11 +1979,18 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
struct btrfs_free_space *info, u64 offset,
- u64 bytes)
+ u64 bytes, enum btrfs_trim_state trim_state)
{
u64 bytes_to_set = 0;
u64 end;
+ /*
+ * This is a tradeoff to make bitmap trim state minimal. We mark the
+ * whole bitmap untrimmed if at any point we add untrimmed regions.
+ */
+ if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED)
+ info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
bytes_to_set = min(end - offset, bytes);
@@ -2058,10 +2065,12 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
struct btrfs_block_group *block_group = NULL;
int added = 0;
u64 bytes, offset, bytes_added;
+ enum btrfs_trim_state trim_state;
int ret;
bytes = info->bytes;
offset = info->offset;
+ trim_state = info->trim_state;
if (!ctl->op->use_bitmap(ctl, info))
return 0;
@@ -2096,8 +2105,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
}
if (entry->offset == offset_to_bitmap(ctl, offset)) {
- bytes_added = add_bytes_to_bitmap(ctl, entry,
- offset, bytes);
+ bytes_added = add_bytes_to_bitmap(ctl, entry, offset,
+ bytes, trim_state);
bytes -= bytes_added;
offset += bytes_added;
}
@@ -2116,7 +2125,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
goto new_bitmap;
}
- bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+ bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+ trim_state);
bytes -= bytes_added;
offset += bytes_added;
added = 0;
@@ -2150,6 +2160,7 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
/* allocate the bitmap */
info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep,
GFP_NOFS);
+ info->trim_state = BTRFS_TRIM_STATE_TRIMMED;
spin_lock(&ctl->tree_lock);
if (!info->bitmap) {
ret = -ENOMEM;
@@ -3320,6 +3331,39 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
return ret;
}
+/*
+ * If we break out of trimming a bitmap prematurely, we should reset the
+ * trimming bit. In a rather contrieved case, it's possible to race here so
+ * reset the state to BTRFS_TRIM_STATE_UNTRIMMED.
+ *
+ * start = start of bitmap
+ * end = near end of bitmap
+ *
+ * Thread 1: Thread 2:
+ * trim_bitmaps(start)
+ * trim_bitmaps(end)
+ * end_trimming_bitmap()
+ * reset_trimming_bitmap()
+ */
+static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
+{
+ struct btrfs_free_space *entry;
+
+ spin_lock(&ctl->tree_lock);
+
+ entry = tree_search_offset(ctl, offset, 1, 0);
+ if (entry)
+ entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+ spin_unlock(&ctl->tree_lock);
+}
+
+static void end_trimming_bitmap(struct btrfs_free_space *entry)
+{
+ if (btrfs_free_space_trimming_bitmap(entry))
+ entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+}
+
static int trim_bitmaps(struct btrfs_block_group *block_group,
u64 *total_trimmed, u64 start, u64 end, u64 minlen)
{
@@ -3344,16 +3388,33 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
}
entry = tree_search_offset(ctl, offset, 1, 0);
- if (!entry) {
+ if (!entry || btrfs_free_space_trimmed(entry)) {
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
next_bitmap = true;
goto next;
}
+ /*
+ * Async discard bitmap trimming begins at by setting the start
+ * to be key.objectid and the offset_to_bitmap() aligns to the
+ * start of the bitmap. This lets us know we are fully
+ * scanning the bitmap rather than only some portion of it.
+ */
+ if (start == offset)
+ entry->trim_state = BTRFS_TRIM_STATE_TRIMMING;
+
bytes = minlen;
ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
if (ret2 || start >= end) {
+ /*
+ * This keeps the invariant that all bytes are trimmed
+ * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap.
+ */
+ if (ret2 && !minlen)
+ end_trimming_bitmap(entry);
+ else
+ entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
next_bitmap = true;
@@ -3362,6 +3423,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
bytes = min(bytes, end - start);
if (bytes < minlen) {
+ entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
goto next;
@@ -3379,18 +3441,21 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
ret = do_trimming(block_group, total_trimmed, start, bytes,
start, bytes, &trim_entry);
- if (ret)
+ if (ret) {
+ reset_trimming_bitmap(ctl, offset);
break;
+ }
next:
if (next_bitmap) {
offset += BITS_PER_BITMAP * ctl->unit;
+ start = offset;
} else {
start += bytes;
- if (start >= offset + BITS_PER_BITMAP * ctl->unit)
- offset += BITS_PER_BITMAP * ctl->unit;
}
if (fatal_signal_pending(current)) {
+ if (start != offset)
+ reset_trimming_bitmap(ctl, offset);
ret = -ERESTARTSYS;
break;
}
@@ -3444,6 +3509,7 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
int btrfs_trim_block_group(struct btrfs_block_group *block_group,
u64 *trimmed, u64 start, u64 end, u64 minlen)
{
+ struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
int ret;
*trimmed = 0;
@@ -3461,6 +3527,9 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
goto out;
ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
+ /* If we ended in the middle of a bitmap, reset the trimming flag. */
+ if (end % (BITS_PER_BITMAP * ctl->unit))
+ reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
out:
btrfs_put_block_group_trimming(block_group);
return ret;
@@ -3645,6 +3714,7 @@ int test_add_free_space_entry(struct btrfs_block_group *cache,
struct btrfs_free_space_ctl *ctl = cache->free_space_ctl;
struct btrfs_free_space *info = NULL, *bitmap_info;
void *map = NULL;
+ enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_TRIMMED;
u64 bytes_added;
int ret;
@@ -3686,7 +3756,8 @@ int test_add_free_space_entry(struct btrfs_block_group *cache,
info = NULL;
}
- bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+ bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+ trim_state);
bytes -= bytes_added;
offset += bytes_added;
@@ -8,10 +8,16 @@
/*
* This is the trim state of an extent or bitmap.
+ *
+ * BTRFS_TRIM_STATE_TRIMMING is special and used to maintain the state of a
+ * bitmap as we may need several trims to fully trim a single bitmap entry.
+ * This is reset should any free space other than trimmed space is added to the
+ * bitmap.
*/
enum btrfs_trim_state {
BTRFS_TRIM_STATE_UNTRIMMED,
BTRFS_TRIM_STATE_TRIMMED,
+ BTRFS_TRIM_STATE_TRIMMING,
};
struct btrfs_free_space {
@@ -29,6 +35,12 @@ static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info)
return (info->trim_state == BTRFS_TRIM_STATE_TRIMMED);
}
+static inline bool btrfs_free_space_trimming_bitmap(
+ struct btrfs_free_space *info)
+{
+ return (info->trim_state == BTRFS_TRIM_STATE_TRIMMING);
+}
+
struct btrfs_free_space_ctl {
spinlock_t tree_lock;
struct rb_root free_space_offset;