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Date: Mon, 22 Jul 2019 12:15:11 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 01/11] ext4: add handling for extended mount options
Unless I missed it, this patch series needs a 00/11 email that describes
*what* "fast commit" is, and why we want it. This should include some
benchmark results, since (I'd assume) that the "fast" part of the feature
name implies a performance improvement?
Cheers, Andreas
> On Jul 21, 2019, at 10:00 PM, Harshad Shirwadkar <harshadshirwadkar@...il.com> wrote:
>
> We are running out of mount option bits. This patch adds handling for
> using s_mount_opt2 and also adds ability to turn on / off the fast
> commit feature. In order to use fast commits, new version e2fsprogs
> needs to set the fast feature commit flag. This also makes sure that
> we have fast commit compatible e2fsprogs before starting to use the
> feature. Mount flag "no_fastcommit", introuced in this patch, can be
> passed to disable the feature at mount time.
>
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> ---
> fs/ext4/ext4.h | 4 ++++
> fs/ext4/super.c | 27 ++++++++++++++++++++++-----
> include/linux/jbd2.h | 5 ++++-
> 3 files changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index bf660aa7a9e0..becbda38b7db 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1146,6 +1146,8 @@ struct ext4_inode_info {
> #define EXT4_MOUNT2_EXPLICIT_JOURNAL_CHECKSUM 0x00000008 /* User explicitly
> specified journal checksum */
>
> +#define EXT4_MOUNT2_JOURNAL_FAST_COMMIT 0x00000010 /* Journal fast commit */
> +
> #define clear_opt(sb, opt) EXT4_SB(sb)->s_mount_opt &= \
> ~EXT4_MOUNT_##opt
> #define set_opt(sb, opt) EXT4_SB(sb)->s_mount_opt |= \
> @@ -1643,6 +1645,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
> #define EXT4_FEATURE_COMPAT_RESIZE_INODE 0x0010
> #define EXT4_FEATURE_COMPAT_DIR_INDEX 0x0020
> #define EXT4_FEATURE_COMPAT_SPARSE_SUPER2 0x0200
> +#define EXT4_FEATURE_COMPAT_FAST_COMMIT 0x0400
>
> #define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001
> #define EXT4_FEATURE_RO_COMPAT_LARGE_FILE 0x0002
> @@ -1743,6 +1746,7 @@ EXT4_FEATURE_COMPAT_FUNCS(xattr, EXT_ATTR)
> EXT4_FEATURE_COMPAT_FUNCS(resize_inode, RESIZE_INODE)
> EXT4_FEATURE_COMPAT_FUNCS(dir_index, DIR_INDEX)
> EXT4_FEATURE_COMPAT_FUNCS(sparse_super2, SPARSE_SUPER2)
> +EXT4_FEATURE_COMPAT_FUNCS(fast_commit, FAST_COMMIT)
>
> EXT4_FEATURE_RO_COMPAT_FUNCS(sparse_super, SPARSE_SUPER)
> EXT4_FEATURE_RO_COMPAT_FUNCS(large_file, LARGE_FILE)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 4079605d437a..e376ac040cce 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1455,6 +1455,7 @@ 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_fastcommit
> };
>
> static const match_table_t tokens = {
> @@ -1537,6 +1538,7 @@ static const match_table_t tokens = {
> {Opt_init_itable, "init_itable=%u"},
> {Opt_init_itable, "init_itable"},
> {Opt_noinit_itable, "noinit_itable"},
> + {Opt_no_fastcommit, "no_fastcommit"},
> {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
> {Opt_test_dummy_encryption, "test_dummy_encryption"},
> {Opt_nombcache, "nombcache"},
> @@ -1659,6 +1661,7 @@ static int clear_qf_name(struct super_block *sb, int qtype)
> #define MOPT_NO_EXT3 0x0200
> #define MOPT_EXT4_ONLY (MOPT_NO_EXT2 | MOPT_NO_EXT3)
> #define MOPT_STRING 0x0400
> +#define MOPT_2 0x0800
>
> static const struct mount_opts {
> int token;
> @@ -1751,6 +1754,8 @@ static const struct mount_opts {
> {Opt_max_dir_size_kb, 0, MOPT_GTE0},
> {Opt_test_dummy_encryption, 0, MOPT_GTE0},
> {Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
> + {Opt_no_fastcommit, EXT4_MOUNT2_JOURNAL_FAST_COMMIT,
> + MOPT_CLEAR | MOPT_2 | MOPT_EXT4_ONLY},
> {Opt_err, 0, 0}
> };
>
> @@ -1858,8 +1863,9 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
> set_opt2(sb, EXPLICIT_DELALLOC);
> } else if (m->mount_opt & EXT4_MOUNT_JOURNAL_CHECKSUM) {
> set_opt2(sb, EXPLICIT_JOURNAL_CHECKSUM);
> - } else
> + } else if (m->mount_opt) {
> return -1;
> + }
> }
> if (m->flags & MOPT_CLEAR_ERR)
> clear_opt(sb, ERRORS_MASK);
> @@ -2027,10 +2033,17 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
> WARN_ON(1);
> return -1;
> }
> - if (arg != 0)
> - sbi->s_mount_opt |= m->mount_opt;
> - else
> - sbi->s_mount_opt &= ~m->mount_opt;
> + if (m->flags & MOPT_2) {
> + if (arg != 0)
> + sbi->s_mount_opt2 |= m->mount_opt;
> + else
> + sbi->s_mount_opt2 &= ~m->mount_opt;
> + } else {
> + if (arg != 0)
> + sbi->s_mount_opt |= m->mount_opt;
> + else
> + sbi->s_mount_opt &= ~m->mount_opt;
> + }
> }
> return 1;
> }
> @@ -3733,6 +3746,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> #ifdef CONFIG_EXT4_FS_POSIX_ACL
> set_opt(sb, POSIX_ACL);
> #endif
> + if (ext4_has_feature_fast_commit(sb))
> + set_opt2(sb, JOURNAL_FAST_COMMIT);
> +
> /* don't forget to enable journal_csum when metadata_csum is enabled. */
> if (ext4_has_metadata_csum(sb))
> set_opt(sb, JOURNAL_CHECKSUM);
> @@ -4334,6 +4350,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> sbi->s_def_mount_opt &= ~EXT4_MOUNT_JOURNAL_CHECKSUM;
> clear_opt(sb, JOURNAL_CHECKSUM);
> clear_opt(sb, DATA_FLAGS);
> + clear_opt2(sb, JOURNAL_FAST_COMMIT);
> sbi->s_journal = NULL;
> needs_recovery = 0;
> goto no_journal;
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index df03825ad1a1..b7eed49b8ecd 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -288,6 +288,7 @@ typedef struct journal_superblock_s
> #define JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT 0x00000004
> #define JBD2_FEATURE_INCOMPAT_CSUM_V2 0x00000008
> #define JBD2_FEATURE_INCOMPAT_CSUM_V3 0x00000010
> +#define JBD2_FEATURE_INCOMPAT_FAST_COMMIT 0x00000020
>
> /* See "journal feature predicate functions" below */
>
> @@ -298,7 +299,8 @@ typedef struct journal_superblock_s
> JBD2_FEATURE_INCOMPAT_64BIT | \
> JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT | \
> JBD2_FEATURE_INCOMPAT_CSUM_V2 | \
> - JBD2_FEATURE_INCOMPAT_CSUM_V3)
> + JBD2_FEATURE_INCOMPAT_CSUM_V3 | \
> + JBD2_FEATURE_INCOMPAT_FAST_COMMIT)
>
> #ifdef __KERNEL__
>
> @@ -1235,6 +1237,7 @@ JBD2_FEATURE_INCOMPAT_FUNCS(64bit, 64BIT)
> JBD2_FEATURE_INCOMPAT_FUNCS(async_commit, ASYNC_COMMIT)
> JBD2_FEATURE_INCOMPAT_FUNCS(csum2, CSUM_V2)
> JBD2_FEATURE_INCOMPAT_FUNCS(csum3, CSUM_V3)
> +JBD2_FEATURE_INCOMPAT_FUNCS(fast_commit, FAST_COMMIT)
>
> /*
> * Journal flag definitions
> --
> 2.22.0.657.g960e92d24f-goog
>
Cheers, Andreas
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