[RFC PATCH v4 34/34] ext4: add mount option for buffered IO iomap path

Zhang Yi
2024-04-10T15:11:54Z

Add buffered_io_iomap mount option to enable buffered IO iomap path for
regular file, this option is disabled by default now.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
fs/ext4/ext4.h | 1 +
fs/ext4/inode.c | 2 ++
fs/ext4/super.c | 16 +++++++++++++++-
3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4e7667b21c2f..fef609e6ba7d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1254,6 +1254,7 @@ struct ext4_inode_info {
* scanning in mballoc
*/
#define EXT4_MOUNT2_ABORT 0x00000100 /* Abort filesystem */
+#define EXT4_MOUNT2_BUFFERED_IOMAP 0x00000200 /* Use iomap for buffered IO */

#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 269503749ef5..c930108f11dd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5120,6 +5120,8 @@ bool ext4_should_use_buffered_iomap(struct inode *inode)
{
struct super_block *sb = inode->i_sb;

+ if (!test_opt2(sb, BUFFERED_IOMAP))
+ return false;
if (ext4_has_feature_inline_data(sb))
return false;
if (ext4_has_feature_verity(sb))
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6410918161a0..c8b691e605f1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1685,7 +1685,7 @@ enum {
Opt_dioread_nolock, Opt_dioread_lock,
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_no_prefetch_block_bitmaps, Opt_mb_optimize_scan, Opt_buffered_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
@@ -1828,6 +1828,7 @@ 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_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 */
@@ -1922,6 +1923,8 @@ 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},
#ifdef CONFIG_EXT4_DEBUG
{Opt_fc_debug_force, EXT4_MOUNT2_JOURNAL_FAST_COMMIT,
MOPT_SET | MOPT_2 | MOPT_EXT4_ONLY},
@@ -2408,6 +2411,11 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
return -EINVAL;
}
return 0;
+ case Opt_buffered_iomap:
+ ext4_msg(NULL, KERN_WARNING,
+ "iomap for buffered enabled. Warning: EXPERIMENTAL, use at your own risk");
+ ctx_set_mount_opt2(ctx, EXT4_MOUNT2_BUFFERED_IOMAP);
+ return 0;
}

/*
@@ -2838,6 +2846,12 @@ static int ext4_check_opt_consistency(struct fs_context *fc,
!(sbi->s_mount_opt2 & EXT4_MOUNT2_DAX_INODE))) {
goto fail_dax_change_remount;
}
+
+ if (ctx_test_mount_opt2(ctx, EXT4_MOUNT2_BUFFERED_IOMAP) &&
+ !test_opt2(sb, BUFFERED_IOMAP)) {
+ ext4_msg(NULL, KERN_ERR, "can't enable iomap for buffered IO on remount");
+ return -EINVAL;
+ }
}

return ext4_check_quota_consistency(fc, sb);
--
2.39.2