btrfs: add missing path cache update during fiemap

Commit Message

Filipe Manana Oct. 3, 2022, 2:57 p.m. UTC

From: Filipe Manana <[e-mail]>

When looking the stored result for a cached path node, if the stored
result is valid and has a value of true, we must update all the nodes for
all levels below it with a result of true as well. This is necessary when
moving from one leaf in the fs tree to the next one, as well as when
moving from a node at any level to the next node at the same level.

Currently this logic is missing as it was somehow forgotten by a recent
patch with the subject: "btrfs: speedup checking for extent sharedness
during fiemap".

This adds the missing logic, which is the counter part to what we do
when adding a shared node to the cache at store_backref_shared_cache().

Signed-off-by: Filipe Manana <[e-mail]>
---
 fs/btrfs/backref.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

David Sterba Oct. 7, 2022, 3:03 p.m. UTC | #1

On Mon, Oct 03, 2022 at 03:57:30PM +0100, [e-mail] wrote:
> From: Filipe Manana <[e-mail]>
> 
> When looking the stored result for a cached path node, if the stored
> result is valid and has a value of true, we must update all the nodes for
> all levels below it with a result of true as well. This is necessary when
> moving from one leaf in the fs tree to the next one, as well as when
> moving from a node at any level to the next node at the same level.
> 
> Currently this logic is missing as it was somehow forgotten by a recent
> patch with the subject: "btrfs: speedup checking for extent sharedness
> during fiemap".
> 
> This adds the missing logic, which is the counter part to what we do
> when adding a shared node to the cache at store_backref_shared_cache().
> 
> Signed-off-by: Filipe Manana <[e-mail]>

Added to misc-next, thanks.

Patch

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index dce3a16996b9..3c0c1f626c75 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1557,6 +1557,19 @@  static bool lookup_backref_shared_cache(struct btrfs_backref_shared_cache *cache
 		return false;
 
 	*is_shared = entry->is_shared;
+	/*
+	 * If the node at this level is shared, than all nodes below are also
+	 * shared. Currently some of the nodes below may be marked as not shared
+	 * because we have just switched from one leaf to another, and switched
+	 * also other nodes above the leaf and below the current level, so mark
+	 * them as shared.
+	 */
+	if (*is_shared) {
+		for (int i = 0; i < level; i++) {
+			cache->entries[i].is_shared = true;
+			cache->entries[i].gen = entry->gen;
+		}
+	}
 
 	return true;
 }