backport 2.2.4 staging for better 6.8 support

[zfsonlinux.git] / debian / patches / 0024-Fix-corruption-caused-by-mmap-flushing-problems.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Robert Evans <rrevans@gmail.com>
Date: Mon, 25 Mar 2024 17:56:49 -0400
Subject: [PATCH] Fix corruption caused by mmap flushing problems

1) Make mmap flushes synchronous. Linux may skip flushing dirty pages
   already in writeback unless data-integrity sync is requested.

2) Change zfs_putpage to use TXG_WAIT. Otherwise dirty pages may be
   skipped due to DMU pushing back on TX assign.

3) Add missing mmap flush when doing block cloning.

4) While here, pass errors from putpage to writepage/writepages.

This change fixes corruption edge cases, but unfortunately adds
synchronous ZIL flushes for dirty mmap pages to llseek and bclone
operations. It may be possible to avoid these sync writes later
but would need more tricky refactoring of the writeback code.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Robert Evans <evansr@google.com>
Closes #15933
Closes #16019
---
 module/os/linux/zfs/zfs_vnops_os.c | 5 +----
 module/os/linux/zfs/zpl_file.c     | 8 ++++----
 module/zfs/zfs_vnops.c             | 6 +++++-
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/module/os/linux/zfs/zfs_vnops_os.c b/module/os/linux/zfs/zfs_vnops_os.c
index c06a75662..7c473bc7e 100644
--- a/module/os/linux/zfs/zfs_vnops_os.c
+++ b/module/os/linux/zfs/zfs_vnops_os.c
@@ -3792,11 +3792,8 @@ zfs_putpage(struct inode *ip, struct page *pp, struct writeback_control *wbc,
 	dmu_tx_hold_sa(tx, zp->z_sa_hdl, B_FALSE);
 	zfs_sa_upgrade_txholds(tx, zp);
 
-	err = dmu_tx_assign(tx, TXG_NOWAIT);
+	err = dmu_tx_assign(tx, TXG_WAIT);
 	if (err != 0) {
-		if (err == ERESTART)
-			dmu_tx_wait(tx);
-
 		dmu_tx_abort(tx);
 #ifdef HAVE_VFS_FILEMAP_DIRTY_FOLIO
 		filemap_dirty_folio(page_mapping(pp), page_folio(pp));
diff --git a/module/os/linux/zfs/zpl_file.c b/module/os/linux/zfs/zpl_file.c
index 3caa0fc6c..9dec52215 100644
--- a/module/os/linux/zfs/zpl_file.c
+++ b/module/os/linux/zfs/zpl_file.c
@@ -720,23 +720,23 @@ zpl_putpage(struct page *pp, struct writeback_control *wbc, void *data)
 {
 	boolean_t *for_sync = data;
 	fstrans_cookie_t cookie;
+	int ret;
 
 	ASSERT(PageLocked(pp));
 	ASSERT(!PageWriteback(pp));
 
 	cookie = spl_fstrans_mark();
-	(void) zfs_putpage(pp->mapping->host, pp, wbc, *for_sync);
+	ret = zfs_putpage(pp->mapping->host, pp, wbc, *for_sync);
 	spl_fstrans_unmark(cookie);
 
-	return (0);
+	return (ret);
 }
 
 #ifdef HAVE_WRITEPAGE_T_FOLIO
 static int
 zpl_putfolio(struct folio *pp, struct writeback_control *wbc, void *data)
 {
-	(void) zpl_putpage(&pp->page, wbc, data);
-	return (0);
+	return (zpl_putpage(&pp->page, wbc, data));
 }
 #endif
 
diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 2b37834d5..7020f88ec 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -130,7 +130,7 @@ zfs_holey_common(znode_t *zp, ulong_t cmd, loff_t *off)
 
 	/* Flush any mmap()'d data to disk */
 	if (zn_has_cached_data(zp, 0, file_sz - 1))
-		zn_flush_cached_data(zp, B_FALSE);
+		zn_flush_cached_data(zp, B_TRUE);
 
 	lr = zfs_rangelock_enter(&zp->z_rangelock, 0, UINT64_MAX, RL_READER);
 	error = dmu_offset_next(ZTOZSB(zp)->z_os, zp->z_id, hole, &noff);
@@ -1193,6 +1193,10 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
 		}
 	}
 
+	/* Flush any mmap()'d data to disk */
+	if (zn_has_cached_data(inzp, inoff, inoff + len - 1))
+		zn_flush_cached_data(inzp, B_TRUE);
+
 	/*
 	 * Maintain predictable lock order.
 	 */