diff mbox series

[15/22] btrfs: limit max discard size for async discard

Message ID 513d7057bfcae4e486c2c62275c1873f6ab256b1.1574709825.git.dennis@kernel.org (mailing list archive)
State New, archived
Headers show
Series btrfs: async discard support | expand

Commit Message

Dennis Zhou Nov. 25, 2019, 7:46 p.m. UTC 
Throttle the maximum size of a discard so that we can provide an upper
bound for the rate of async discard. While the block layer is able to
split discards into the appropriate sized discards, we want to be able
to account more accurately the rate at which we are consuming ncq slots
as well as limit the upper bound of work for a discard.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/discard.h          |  5 ++++
 fs/btrfs/free-space-cache.c | 48 +++++++++++++++++++++++++++----------
 2 files changed, 41 insertions(+), 12 deletions(-)
diff mbox series

Patch

diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index 88f1363aa4e4..e1819f319901 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -3,10 +3,15 @@ 
 #ifndef BTRFS_DISCARD_H
 #define BTRFS_DISCARD_H
 
+#include <linux/sizes.h>
+
 struct btrfs_fs_info;
 struct btrfs_discard_ctl;
 struct btrfs_block_group;
 
+/* Discard size limits. */
+#define BTRFS_ASYNC_DISCARD_MAX_SIZE	(SZ_64M)
+
 /* List operations. */
 void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 5655416f0ae7..452afd616623 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3442,19 +3442,40 @@  static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		if (entry->offset >= end)
 			goto out_unlock;
 
-		extent_start = entry->offset;
-		extent_bytes = entry->bytes;
-		extent_trim_state = entry->trim_state;
-		start = max(start, extent_start);
-		bytes = min(extent_start + extent_bytes, end) - start;
-		if (bytes < minlen) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			goto next;
-		}
+		if (async) {
+			start = extent_start = entry->offset;
+			bytes = extent_bytes = entry->bytes;
+			extent_trim_state = entry->trim_state;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
+			unlink_free_space(ctl, entry);
+			if (bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) {
+				bytes = extent_bytes =
+					BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				entry->offset += BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				entry->bytes -= BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				link_free_space(ctl, entry);
+			} else {
+				kmem_cache_free(btrfs_free_space_cachep, entry);
+			}
+		} else {
+			extent_start = entry->offset;
+			extent_bytes = entry->bytes;
+			extent_trim_state = entry->trim_state;
+			start = max(start, extent_start);
+			bytes = min(extent_start + extent_bytes, end) - start;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
 
-		unlink_free_space(ctl, entry);
-		kmem_cache_free(btrfs_free_space_cachep, entry);
+			unlink_free_space(ctl, entry);
+			kmem_cache_free(btrfs_free_space_cachep, entry);
+		}
 
 		spin_unlock(&ctl->tree_lock);
 		trim_entry.start = extent_start;
@@ -3619,6 +3640,9 @@  static int trim_bitmaps(struct btrfs_block_group *block_group,
 			goto next;
 		}
 
+		if (async && bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE)
+			bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE;
+
 		bitmap_clear_bits(ctl, entry, start, bytes);
 		if (entry->bytes == 0)
 			free_bitmap(ctl, entry);