linux-ext4 - [PATCH 1/2] ext4: remove extent cache entries when truncating inline data

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Date:   Thu, 19 Aug 2021 10:49:26 -0400
From:   Eric Whitney <enwlinux@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu, Eric Whitney <enwlinux@...il.com>
Subject: [PATCH 1/2] ext4: remove extent cache entries when truncating inline data

Conditionally remove all cached extents belonging to an inode
when truncating its inline data.  It's only necessary to attempt to
remove cached extents when a conversion from inline to extent storage
has been initiated (!EXT4_STATE_MAY_INLINE_DATA).  This avoids
unnecessary es lock overhead in the more common inline case.

Signed-off-by: Eric Whitney <enwlinux@...il.com>
---
 fs/ext4/inline.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 70cb64db33f7..49b0b4fcea6d 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -7,6 +7,7 @@
 #include <linux/iomap.h>
 #include <linux/fiemap.h>
 #include <linux/iversion.h>
+#include <linux/backing-dev.h>
 
 #include "ext4_jbd2.h"
 #include "ext4.h"
@@ -1903,6 +1904,24 @@ int ext4_inline_data_truncate(struct inode *inode, int *has_inline)
 	EXT4_I(inode)->i_disksize = i_size;
 
 	if (i_size < inline_size) {
+		/*
+		 * if there's inline data to truncate and this file was
+		 * converted to extents after that inline data was written,
+		 * the extent status cache must be cleared to avoid leaving
+		 * behind stale delayed allocated extent entries
+		 */
+		if (!ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
+retry:
+			err = ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);
+			if (err == -ENOMEM) {
+				cond_resched();
+				congestion_wait(BLK_RW_ASYNC, HZ/50);
+				goto retry;
+			}
+			if (err)
+				goto out_error;
+		}
+
 		/* Clear the content in the xattr space. */
 		if (inline_size > EXT4_MIN_INLINE_DATA_SIZE) {
 			if ((err = ext4_xattr_ibody_find(inode, &i, &is)) != 0)
-- 
2.20.1