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Wong" , Christoph Hellwig , John Garry , Ojaswin Mujoo , Dave Chinner , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Ritesh Harjani (IBM)" Subject: [PATCH v3 1/4] ext4: Add statx support for atomic writes Date: Wed, 30 Oct 2024 21:27:38 +0530 Message-ID: <3338514d98370498d49ebc297a9b6d48a55282b8.1730286164.git.ritesh.list@gmail.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This patch adds base support for atomic writes via statx getattr. On bs < ps systems, we can create FS with say bs of 16k. That means both atomic write min and max unit can be set to 16k for supporting atomic writes. Co-developed-by: Ojaswin Mujoo Signed-off-by: Ojaswin Mujoo Signed-off-by: Ritesh Harjani (IBM) --- fs/ext4/ext4.h | 9 +++++++++ fs/ext4/inode.c | 14 ++++++++++++++ fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++ 3 files changed, 54 insertions(+) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 44b0d418143c..6ee49aaacd2b 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1729,6 +1729,10 @@ struct ext4_sb_info { */ struct work_struct s_sb_upd_work; =20 + /* Atomic write unit values in bytes */ + unsigned int s_awu_min; + unsigned int s_awu_max; + /* Ext4 fast commit sub transaction ID */ atomic_t s_fc_subtid; =20 @@ -3855,6 +3859,11 @@ static inline int ext4_buffer_uptodate(struct buffer= _head *bh) return buffer_uptodate(bh); } =20 +static inline bool ext4_can_atomic_write(struct super_block *sb) +{ + return EXT4_SB(sb)->s_awu_min > 0; +} + extern int ext4_block_write_begin(handle_t *handle, struct folio *folio, loff_t pos, unsigned len, get_block_t *get_block); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 54bdd4884fe6..fcdee27b9aa2 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5578,6 +5578,20 @@ int ext4_getattr(struct mnt_idmap *idmap, const stru= ct path *path, } } =20 + if (S_ISREG(inode->i_mode) && (request_mask & STATX_WRITE_ATOMIC)) { + struct ext4_sb_info *sbi =3D EXT4_SB(inode->i_sb); + unsigned int awu_min, awu_max; + + if (ext4_can_atomic_write(inode->i_sb)) { + awu_min =3D sbi->s_awu_min; + awu_max =3D sbi->s_awu_max; + } else { + awu_min =3D awu_max =3D 0; + } + + generic_fill_statx_atomic_writes(stat, awu_min, awu_max); + } + flags =3D ei->i_flags & EXT4_FL_USER_VISIBLE; if (flags & EXT4_APPEND_FL) stat->attributes |=3D STATX_ATTR_APPEND; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 16a4ce704460..ebe1660bd840 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_bloc= k *sb) return 0; } =20 +/* + * ext4_atomic_write_init: Initializes filesystem min & max atomic write u= nits. + * @sb: super block + * TODO: Later add support for bigalloc + */ +static void ext4_atomic_write_init(struct super_block *sb) +{ + struct ext4_sb_info *sbi =3D EXT4_SB(sb); + struct block_device *bdev =3D sb->s_bdev; + + if (!bdev_can_atomic_write(bdev)) + return; + + if (!ext4_has_feature_extents(sb)) + return; + + sbi->s_awu_min =3D max(sb->s_blocksize, + bdev_atomic_write_unit_min_bytes(bdev)); + sbi->s_awu_max =3D min(sb->s_blocksize, + bdev_atomic_write_unit_max_bytes(bdev)); + if (sbi->s_awu_min && sbi->s_awu_max && + sbi->s_awu_min <=3D sbi->s_awu_max) { + ext4_msg(sb, KERN_NOTICE, "Supports (experimental) DIO atomic writes awu= _min: %u, awu_max: %u", + sbi->s_awu_min, sbi->s_awu_max); + } else { + sbi->s_awu_min =3D 0; + sbi->s_awu_max =3D 0; + } +} + static void ext4_fast_commit_init(struct super_block *sb) { struct ext4_sb_info *sbi =3D EXT4_SB(sb); @@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, s= truct super_block *sb) =20 spin_lock_init(&sbi->s_bdev_wb_lock); =20 + ext4_atomic_write_init(sb); ext4_fast_commit_init(sb); =20 sb->s_root =3D NULL; --=20 2.46.0