[PATCH v3 18/22] ext4: introduce a mount option for iomap buffered I/O path

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

Since the iomap buffered I/O path does not yet support all existing
features, it cannot be enabled by default. Introduce 'buffered_iomap'
and 'nobuffered_iomap' mount options to enable and disable the iomap
buffered I/O path for regular files.

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/ext4/ext4.h  | 1 +
 fs/ext4/inode.c | 2 ++
 fs/ext4/super.c | 7 +++++++
 3 files changed, 10 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 80d086d40990..60ba488b01c5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1281,6 +1281,7 @@ struct ext4_inode_info {
 						    * scanning in mballoc
 						    */
 #define EXT4_MOUNT2_ABORT		0x00000100 /* Abort filesystem */
+#define EXT4_MOUNT2_BUFFERED_IOMAP	0x00000200 /* Use iomap for buffered I/O */
 
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
 						~EXT4_MOUNT_##opt
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 57b5708235cf..d2f7af7922d7 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5750,6 +5750,8 @@ void ext4_enable_buffered_iomap(struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
 
+	if (!test_opt2(sb, BUFFERED_IOMAP))
+		return;
 	if (!S_ISREG(inode->i_mode))
 		return;
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE))
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 62bfe05a64bc..b2da4834b6bb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1722,6 +1722,7 @@ enum {
 	Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
 	Opt_max_dir_size_kb, Opt_nojournal_checksum, Opt_nombcache,
 	Opt_no_prefetch_block_bitmaps, Opt_mb_optimize_scan,
+	Opt_buffered_iomap, Opt_nobuffered_iomap,
 	Opt_errors, Opt_data, Opt_data_err, Opt_jqfmt, Opt_dax_type,
 #ifdef CONFIG_EXT4_DEBUG
 	Opt_fc_debug_max_replay, Opt_fc_debug_force
@@ -1860,6 +1861,8 @@ static const struct fs_parameter_spec ext4_param_specs[] = {
 	fsparam_flag	("no_prefetch_block_bitmaps",
 						Opt_no_prefetch_block_bitmaps),
 	fsparam_s32	("mb_optimize_scan",	Opt_mb_optimize_scan),
+	fsparam_flag	("buffered_iomap",	Opt_buffered_iomap),
+	fsparam_flag	("nobuffered_iomap",	Opt_nobuffered_iomap),
 	fsparam_string	("check",		Opt_removed),	/* mount option from ext2/3 */
 	fsparam_flag	("nocheck",		Opt_removed),	/* mount option from ext2/3 */
 	fsparam_flag	("reservation",		Opt_removed),	/* mount option from ext2/3 */
@@ -1953,6 +1956,10 @@ static const struct mount_opts {
 	{Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
 	{Opt_no_prefetch_block_bitmaps, EXT4_MOUNT_NO_PREFETCH_BLOCK_BITMAPS,
 	 MOPT_SET},
+	{Opt_buffered_iomap, EXT4_MOUNT2_BUFFERED_IOMAP,
+	 MOPT_SET | MOPT_2 | MOPT_EXT4_ONLY},
+	{Opt_nobuffered_iomap, EXT4_MOUNT2_BUFFERED_IOMAP,
+	 MOPT_CLEAR | MOPT_2 | MOPT_EXT4_ONLY},
 #ifdef CONFIG_EXT4_DEBUG
 	{Opt_fc_debug_force, EXT4_MOUNT2_JOURNAL_FAST_COMMIT,
 	 MOPT_SET | MOPT_2 | MOPT_EXT4_ONLY},
-- 
2.52.0