On 6/15/26 8:05 PM, Chao Yu via Linux-f2fs-devel wrote:
On 6/12/26 19:58, Yongpeng Yang wrote:
From: Yongpeng Yang <[email protected]>
Previously, when an extent being inserted overlaps with the largest
extent, the largest extent is dropped entirely. This was done to handle
Please correct me if I missed anything, I remember that we will add largest
extent in below path?
- __update_extent_tree_range
- __insert_extent_tree
- __try_update_largest_extent : update largest w/ right extent
- __try_update_largest_extent : update largest w/ left extent
The largest extent might not reside in the extent tree. If
__update_extent_tree_range invokes __drop_largest_extent, the length of
the largest extent will have been set to zero. As a result, the largest
extent updated inside __try_update_largest_extent can end up smaller
than the largest extent obtained after __punch_largest_extent completes
its punch operation.
Thanks
Yongpeng,
Thanks,
the case where the largest extent is not in memory, avoiding
inconsistency between the largest extent and the extent tree.
This patch changes the semantics of __drop_largest_extent (renamed to
__punch_largest_extent): instead of discarding the entire largest
extent when any overlap is detected, keep the larger remaining portion
(left or right) after the punch. This preserves extent cache coverage
for truncate and overwrite operations that only partially overlap the
largest extent.
Signed-off-by: Yongpeng Yang <[email protected]>
---
fs/f2fs/extent_cache.c | 31 ++++++++++++++++++++++++-------
1 file changed, 24 insertions(+), 7 deletions(-)
diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index f8d94db60dc6..82d84c4e98b2 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -397,14 +397,31 @@ static unsigned int __free_extent_tree(struct
f2fs_sb_info *sbi,
return count;
}
-static void __drop_largest_extent(struct extent_tree *et,
+static void __punch_largest_extent(struct extent_tree *et,
pgoff_t fofs, unsigned int len)
{
- if (fofs < (pgoff_t)et->largest.fofs + et->largest.len &&
- fofs + len > et->largest.fofs) {
- et->largest.len = 0;
- et->largest_updated = true;
+ unsigned int largest_end, punch_end;
+ unsigned int left_len, right_len;
+
+ if (fofs >= (pgoff_t)et->largest.fofs + et->largest.len ||
+ fofs + len <= et->largest.fofs)
+ return;
+
+ /* Punch [fofs, fofs + len) from largest extent. */
+ largest_end = et->largest.fofs + et->largest.len;
+ punch_end = fofs + len;
+
+ left_len = fofs > et->largest.fofs ? fofs - et->largest.fofs : 0;
+ right_len = largest_end > punch_end ? largest_end - punch_end : 0;
+
+ if (left_len >= right_len) {
+ et->largest.len = left_len;
+ } else {
+ et->largest.blk += punch_end - et->largest.fofs;
+ et->largest.fofs = punch_end;
+ et->largest.len = right_len;
}
+ et->largest_updated = true;
}
void f2fs_init_read_extent_tree(struct inode *inode, struct folio *ifolio)
@@ -680,10 +697,10 @@ static void __update_extent_tree_range(struct inode
*inode,
dei.len = 0;
/*
- * drop largest extent before lookup, in case it's already
+ * punch largest extent before lookup, in case it's already
* been shrunk from extent tree
*/
- __drop_largest_extent(et, fofs, len);
+ __punch_largest_extent(et, fofs, len);
}
if (et->largest.len != 0 &&
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