ext4: Add atomic writes support for DIO

PATCH In review Ritesh Harjani (IBM) 5 participants 14 messages Nov 1, 2024 – Nov 2, 2024

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VFS ext4 file system

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Ritesh Harjani (IBM)

author reviewer

2024-11-01 06:51 UTC #0 lore raw

v4 cover ext4: Add atomic writes support for DIO

v3 -> v4:
=========
1. Patch-1 changes the helper function from ext4_can_atomic_write() to ext4_inode_can_atomic_write() based on suggestions from Darrick and John. Patch-3 then goes and uses it.
2. Patch-4 adds an inline helper ext4_want_directio_fallback() which simplifies the logic checks and inherently fixes condition on when to return -ENOTBLK which otherwise was always returning true for any write or directio in ext4_iomap_end(). It was ok since ext4 only supports direct-io via iomap.
[v3]: https://lore.kernel.org/linux-xfs/[email protected]/

(Note as mentioned below as well this is built on top of John XFS atomic series [2]) [2]: https://lore.kernel.org/linux-xfs/[email protected]/

v2 -> v3:
==========
1. Patch-1 adds an "experimental" string in dmesg log during mount when EXT4 detects that it is capable of doing DIO atomic writes on a given device with min and max unit details.
2. Patch-4 has been updated to avoid returning -ENOTBLK (in ext4_iomap_end) if the request belongs to atomic write. This patch also adds a WARN_ON_ONCE() if atomic write ever fallback to buffered-io (to catch any unwanted bugs in the future). More details in the commit log of patch-4.
3. Collected RBs tag from John for Patch 2 & 3.

[v2]: https://lore.kernel.org/linux-ext4/[email protected]/

Previous cover letter log:

In v2, we had split the series and this one only takes care of atomic writes for single fsblock.
That means for now this gets only enabled on bs < ps systems on ext4. Enablement of atomic writes for bigalloc (multi-fsblock support) is still under discussion and may require general consensus within the filesystem community [1].

This series adds the base feature support to enable atomic writes in direct-io path for ext4. We advertise the minimum and the maximum atomic write unit sizes via statx on a regular file.

This series allows users to utilize atomic write support using -
1. on bs < ps systems via - mkfs.ext4 -F -b 16384 /dev/sda

This can then be utilized using -

	xfs_io -fdc "pwrite -V 1 -A -b16k 0 16k" /mnt/f1

This is built on top of John's DIO atomic write series for XFS [2]. The VFS and block layer enablement for atomic writes were merged already.

[1]: https://lore.kernel.org/linux-ext4/[email protected]
[2]: https://lore.kernel.org/linux-xfs/[email protected]/

Changelogs:
===========
PATCH -> PATCH v2:
- addressed review comments from John and Darrick.
- renamed ext4_sb_info variables names: fs_awu* -> s_awu*
- [PATCH]: https://lore.kernel.org/linux-ext4/[email protected]/

RFC -> PATCH:
- Dropped RFC tag
- Last RFC was posted a while ago but back then a lot of VFS and block layer interfaces were still not merged. Those are now merged, thanks to John and everyone else.
- [RFC] - https://lore.kernel.org/linux-ext4/[email protected]/

Ritesh Harjani (IBM) (4):
ext4: Add statx support for atomic writes
ext4: Check for atomic writes support in write iter
ext4: Support setting FMODE_CAN_ATOMIC_WRITE
ext4: Do not fallback to buffered-io for DIO atomic write

 fs/ext4/ext4.h  | 10 ++++++++++
 fs/ext4/file.c  | 24 ++++++++++++++++++++++++
 fs/ext4/inode.c | 39 ++++++++++++++++++++++++++++++++++-----
 fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
 4 files changed, 99 insertions(+), 5 deletions(-)

--
2.46.0

Ritesh Harjani (IBM)

author reviewer

2024-11-01 06:51 UTC #1 lore raw

PATCH v4 1/4 ext4: Add statx support for atomic writes

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 <[email protected]>

Signed-off-by Ojaswin Mujoo <[email protected]>

Signed-off-by Ritesh Harjani (IBM) <[email protected]>

---
 fs/ext4/ext4.h  | 10 ++++++++++
 fs/ext4/inode.c | 12 ++++++++++++
 fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

fs/ext4/ext4.h +10 -0

index 44b0d418143c..494d443e9fc9 100644
@@ -1729,6 +1729,10 @@ struct ext4_sb_info {
 	 */
 	struct work_struct s_sb_upd_work;
 
+	/* 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;

@@ -3855,6 +3859,12 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
 	return buffer_uptodate(bh);
 }
 
+static inline bool ext4_inode_can_atomic_write(struct inode *inode)
+{
+
+	return S_ISREG(inode->i_mode) && EXT4_SB(inode->i_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);

fs/ext4/inode.c +12 -0

index 54bdd4884fe6..3e827cfa762e 100644
@@ -5578,6 +5578,18 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
 		}
 	}
 
+	if ((request_mask & STATX_WRITE_ATOMIC) && S_ISREG(inode->i_mode)) {
+		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+		unsigned int awu_min = 0, awu_max = 0;
+
+		if (ext4_inode_can_atomic_write(inode)) {
+			awu_min = sbi->s_awu_min;
+			awu_max = sbi->s_awu_max;
+		}
+
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+	}
+
 	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
 	if (flags & EXT4_APPEND_FL)
 		stat->attributes |= STATX_ATTR_APPEND;

fs/ext4/super.c +31 -0

index 16a4ce704460..ebe1660bd840 100644
@@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_block *sb)
 	return 0;
 }
 
+/*
+ * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * @sb: super block
+ * TODO: Later add support for bigalloc
+ */
+static void ext4_atomic_write_init(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+
+	if (!bdev_can_atomic_write(bdev))
+		return;
+
+	if (!ext4_has_feature_extents(sb))
+		return;
+
+	sbi->s_awu_min = max(sb->s_blocksize,
+			      bdev_atomic_write_unit_min_bytes(bdev));
+	sbi->s_awu_max = min(sb->s_blocksize,
+			      bdev_atomic_write_unit_max_bytes(bdev));
+	if (sbi->s_awu_min && sbi->s_awu_max &&
+	    sbi->s_awu_min <= 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 = 0;
+		sbi->s_awu_max = 0;
+	}
+}
+
 static void ext4_fast_commit_init(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
 	spin_lock_init(&sbi->s_bdev_wb_lock);
 
+	ext4_atomic_write_init(sb);
 	ext4_fast_commit_init(sb);
 
 	sb->s_root = NULL;

Signature · 1 line

2.46.0

Ritesh Harjani (IBM)

author reviewer

2024-11-01 06:51 UTC #6 lore raw

PATCH v4 2/4 ext4: Check for atomic writes support in write iter

In reply to Ritesh Harjani (IBM)

Let's validate the given constraints for atomic write request. Otherwise it will fail with -EINVAL. Currently atomic write is only supported on DIO, so for buffered-io it will return -EOPNOTSUPP.

Reviewed-by John Garry <[email protected]>

Reviewed-by Darrick J. Wong <[email protected]>

Signed-off-by Ritesh Harjani (IBM) <[email protected]>

---
 fs/ext4/file.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

fs/ext4/file.c +14 -0

index f14aed14b9cf..a7b9b9751a3f 100644
@@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (IS_DAX(inode))
 		return ext4_dax_write_iter(iocb, from);
 #endif
+
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		size_t len = iov_iter_count(from);
+		int ret;
+
+		if (len < EXT4_SB(inode->i_sb)->s_awu_min ||
+		    len > EXT4_SB(inode->i_sb)->s_awu_max)
+			return -EINVAL;
+
+		ret = generic_atomic_write_valid(iocb, from);
+		if (ret)
+			return ret;
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT)
 		return ext4_dio_write_iter(iocb, from);
 	else

--
2.46.0

Ritesh Harjani (IBM)

author reviewer

2024-11-01 06:51 UTC #8 lore raw

PATCH v4 3/4 ext4: Support setting FMODE_CAN_ATOMIC_WRITE

In reply to Ritesh Harjani (IBM)

FS needs to add the fmode capability in order to support atomic writes during file open (refer kiocb_set_rw_flags()). Set this capability on a regular file if ext4 can do atomic write.

Reviewed-by John Garry <[email protected]>

Reviewed-by Darrick J. Wong <[email protected]>

Signed-off-by Ritesh Harjani (IBM) <[email protected]>

---
 fs/ext4/file.c | 3 +++
 1 file changed, 3 insertions(+)

fs/ext4/file.c +3 -0

index a7b9b9751a3f..96d936f5584b 100644
@@ -898,6 +898,9 @@ static int ext4_file_open(struct inode *inode, struct file *filp)
 			return ret;
 	}
 
+	if (ext4_inode_can_atomic_write(inode))
+		filp->f_mode |= FMODE_CAN_ATOMIC_WRITE;
+
 	filp->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
 	return dquot_file_open(inode, filp);
 }

--
2.46.0

Ritesh Harjani (IBM)

author reviewer

2024-11-01 06:51 UTC #10 lore raw

PATCH v4 4/4 ext4: Do not fallback to buffered-io for DIO atomic write

In reply to Ritesh Harjani (IBM)

atomic writes is currently only supported for single fsblock and only for direct-io. We should not return -ENOTBLK for atomic writes since we want the atomic write request to either complete fully or fail otherwise. Hence, we should never fallback to buffered-io in case of DIO atomic write requests.
Let's also catch if this ever happens by adding some WARN_ON_ONCE before buffered-io handling for direct-io atomic writes. More details of the discussion [1].

While at it let's add an inline helper ext4_want_directio_fallback() which simplifies the logic checks and inherently fixes condition on when to return -ENOTBLK which otherwise was always returning true for any write or directio in ext4_iomap_end(). It was ok since ext4 only supports direct-io via iomap.

[1]: https://lore.kernel.org/linux-xfs/[email protected]/T/#m9dbecc11bed713ed0d7a486432c56b105b555f04

Signed-off-by Ritesh Harjani (IBM) <[email protected]>

---
 fs/ext4/file.c  |  7 +++++++
 fs/ext4/inode.c | 27 ++++++++++++++++++++++-----
 2 files changed, 29 insertions(+), 5 deletions(-)

fs/ext4/file.c +7 -0

index 96d936f5584b..a7de03e47db0 100644
@@ -599,6 +599,13 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		ssize_t err;
 		loff_t endbyte;
 
+		/*
+		 * There is no support for atomic writes on buffered-io yet,
+		 * we should never fallback to buffered-io for DIO atomic
+		 * writes.
+		 */
+		WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC);
+
 		offset = iocb->ki_pos;
 		err = ext4_buffered_write_iter(iocb, from);
 		if (err < 0)

fs/ext4/inode.c +22 -5

index 3e827cfa762e..5b9eeb74ce47 100644
@@ -3444,17 +3444,34 @@ static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset,
 	return ret;
 }
 
+static inline bool ext4_want_directio_fallback(unsigned flags, ssize_t written)
+{
+	/* must be a directio to fall back to buffered */
+	if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) !=
+		    (IOMAP_WRITE | IOMAP_DIRECT))
+		return false;
+
+	/* atomic writes are all-or-nothing */
+	if (flags & IOMAP_ATOMIC)
+		return false;
+
+	/* can only try again if we wrote nothing */
+	return written == 0;
+}
+
 static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
 			  ssize_t written, unsigned flags, struct iomap *iomap)
 {
 	/*
 	 * Check to see whether an error occurred while writing out the data to
-	 * the allocated blocks. If so, return the magic error code so that we
-	 * fallback to buffered I/O and attempt to complete the remainder of
-	 * the I/O. Any blocks that may have been allocated in preparation for
-	 * the direct I/O will be reused during buffered I/O.
+	 * the allocated blocks. If so, return the magic error code for
+	 * non-atomic write so that we fallback to buffered I/O and attempt to
+	 * complete the remainder of the I/O.
+	 * For non-atomic writes, any blocks that may have been
+	 * allocated in preparation for the direct I/O will be reused during
+	 * buffered I/O. For atomic write, we never fallback to buffered-io.
 	 */
-	if (flags & (IOMAP_WRITE | IOMAP_DIRECT) && written == 0)
+	if (ext4_want_directio_fallback(flags, written))
 		return -ENOTBLK;
 
 	return 0;

--
2.46.0

Jan Kara

reviewer Reviewed-by on v4 4/4

2024-11-01 11:13 UTC #11 lore raw

Re: [PATCH v4 4/4] ext4: Do not fallback to buffered-io for DIO atomic write

Quoted 9 lines · Ritesh Harjani (IBM)

atomic writes is currently only supported for single fsblock and only for direct-io. We should not return -ENOTBLK for atomic writes since we want the atomic write request to either complete fully or fail otherwise. Hence, we should never fallback to buffered-io in case of DIO atomic write requests.
Let's also catch if this ever happens by adding some WARN_ON_ONCE before buffered-io handling for direct-io atomic writes. More details of the discussion [1].

Quoted 8 lines

While at it let's add an inline helper ext4_want_directio_fallback() which simplifies the logic checks and inherently fixes condition on when to return -ENOTBLK which otherwise was always returning true for any write or directio in ext4_iomap_end(). It was ok since ext4 only supports direct-io via iomap.
[1]: https://lore.kernel.org/linux-xfs/[email protected]/T/#m9dbecc11bed713ed0d7a486432c56b105b555f04
Suggested-by Darrick J. Wong <[email protected]> # inline helper
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

Looks good. Feel free to add:

Reviewed-by Jan Kara <[email protected]>

Honza

Quoted 70 lines

---
 fs/ext4/file.c  |  7 +++++++
 fs/ext4/inode.c | 27 ++++++++++++++++++++++-----
 2 files changed, 29 insertions(+), 5 deletions(-)

fs/ext4/file.c +7 -0

index 96d936f5584b..a7de03e47db0 100644
@@ -599,6 +599,13 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		ssize_t err;
 		loff_t endbyte;
 
+		/*
+		 * There is no support for atomic writes on buffered-io yet,
+		 * we should never fallback to buffered-io for DIO atomic
+		 * writes.
+		 */
+		WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC);
+
 		offset = iocb->ki_pos;
 		err = ext4_buffered_write_iter(iocb, from);
 		if (err < 0)

fs/ext4/inode.c +22 -6

index 3e827cfa762e..5b9eeb74ce47 100644
@@ -3444,17 +3444,34 @@ static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset,
 	return ret;
 }
 
+static inline bool ext4_want_directio_fallback(unsigned flags, ssize_t written)
+{
+	/* must be a directio to fall back to buffered */
+	if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) !=
+		    (IOMAP_WRITE | IOMAP_DIRECT))
+		return false;
+
+	/* atomic writes are all-or-nothing */
+	if (flags & IOMAP_ATOMIC)
+		return false;
+
+	/* can only try again if we wrote nothing */
+	return written == 0;
+}
+
 static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
 			  ssize_t written, unsigned flags, struct iomap *iomap)
 {
 	/*
 	 * Check to see whether an error occurred while writing out the data to
-	 * the allocated blocks. If so, return the magic error code so that we
-	 * fallback to buffered I/O and attempt to complete the remainder of
-	 * the I/O. Any blocks that may have been allocated in preparation for
-	 * the direct I/O will be reused during buffered I/O.
+	 * the allocated blocks. If so, return the magic error code for
+	 * non-atomic write so that we fallback to buffered I/O and attempt to
+	 * complete the remainder of the I/O.
+	 * For non-atomic writes, any blocks that may have been
+	 * allocated in preparation for the direct I/O will be reused during
+	 * buffered I/O. For atomic write, we never fallback to buffered-io.
 	 */
-	if (flags & (IOMAP_WRITE | IOMAP_DIRECT) && written == 0)
+	if (ext4_want_directio_fallback(flags, written))
 		return -ENOTBLK;
 
 	return 0;
--

2.46.0

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Jan Kara

reviewer Reviewed-by on v4 3/4

2024-11-01 11:14 UTC #9 lore raw

Re: [PATCH v4 3/4] ext4: Support setting FMODE_CAN_ATOMIC_WRITE

In reply to Ritesh Harjani (IBM)

Quoted 7 lines · Ritesh Harjani (IBM)

FS needs to add the fmode capability in order to support atomic writes during file open (refer kiocb_set_rw_flags()). Set this capability on a regular file if ext4 can do atomic write.
Reviewed-by John Garry <[email protected]>
Reviewed-by Darrick J. Wong <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

Looks good. Feel free to add:

Reviewed-by Jan Kara <[email protected]>

Honza

Quoted 21 lines

---
 fs/ext4/file.c | 3 +++
 1 file changed, 3 insertions(+)

fs/ext4/file.c +3 -1

index a7b9b9751a3f..96d936f5584b 100644
@@ -898,6 +898,9 @@ static int ext4_file_open(struct inode *inode, struct file *filp)
 			return ret;
 	}
 
+	if (ext4_inode_can_atomic_write(inode))
+		filp->f_mode |= FMODE_CAN_ATOMIC_WRITE;
+
 	filp->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
 	return dquot_file_open(inode, filp);
 }
--

2.46.0

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Jan Kara

reviewer Reviewed-by on v4 2/4

2024-11-01 11:15 UTC #7 lore raw

Re: [PATCH v4 2/4] ext4: Check for atomic writes support in write iter

In reply to Ritesh Harjani (IBM)

Quoted 7 lines · Ritesh Harjani (IBM)

Let's validate the given constraints for atomic write request. Otherwise it will fail with -EINVAL. Currently atomic write is only supported on DIO, so for buffered-io it will return -EOPNOTSUPP.
Reviewed-by John Garry <[email protected]>
Reviewed-by Darrick J. Wong <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

Looks good. Feel free to add:

Reviewed-by Jan Kara <[email protected]>

Honza

Quoted 32 lines

---
 fs/ext4/file.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

fs/ext4/file.c +14 -1

index f14aed14b9cf..a7b9b9751a3f 100644
@@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (IS_DAX(inode))
 		return ext4_dax_write_iter(iocb, from);
 #endif
+
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		size_t len = iov_iter_count(from);
+		int ret;
+
+		if (len < EXT4_SB(inode->i_sb)->s_awu_min ||
+		    len > EXT4_SB(inode->i_sb)->s_awu_max)
+			return -EINVAL;
+
+		ret = generic_atomic_write_valid(iocb, from);
+		if (ret)
+			return ret;
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT)
 		return ext4_dio_write_iter(iocb, from);
 	else
--

2.46.0

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Jan Kara

reviewer Reviewed-by on v4 1/4

2024-11-01 11:17 UTC #2 lore raw

Re: [PATCH v4 1/4] ext4: Add statx support for atomic writes

In reply to Ritesh Harjani (IBM)

Quoted 8 lines · Ritesh Harjani (IBM)

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 <[email protected]>
Signed-off-by Ojaswin Mujoo <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

I guess this is a good start. Feel free to add:

Reviewed-by Jan Kara <[email protected]>

Honza

Quoted 109 lines

---
 fs/ext4/ext4.h  | 10 ++++++++++
 fs/ext4/inode.c | 12 ++++++++++++
 fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

fs/ext4/ext4.h +10 -0

index 44b0d418143c..494d443e9fc9 100644
@@ -1729,6 +1729,10 @@ struct ext4_sb_info {
 	 */
 	struct work_struct s_sb_upd_work;
 
+	/* 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;

@@ -3855,6 +3859,12 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
 	return buffer_uptodate(bh);
 }
 
+static inline bool ext4_inode_can_atomic_write(struct inode *inode)
+{
+
+	return S_ISREG(inode->i_mode) && EXT4_SB(inode->i_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);

fs/ext4/inode.c +12 -0

index 54bdd4884fe6..3e827cfa762e 100644
@@ -5578,6 +5578,18 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
 		}
 	}
 
+	if ((request_mask & STATX_WRITE_ATOMIC) && S_ISREG(inode->i_mode)) {
+		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+		unsigned int awu_min = 0, awu_max = 0;
+
+		if (ext4_inode_can_atomic_write(inode)) {
+			awu_min = sbi->s_awu_min;
+			awu_max = sbi->s_awu_max;
+		}
+
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+	}
+
 	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
 	if (flags & EXT4_APPEND_FL)
 		stat->attributes |= STATX_ATTR_APPEND;

fs/ext4/super.c +31 -0

index 16a4ce704460..ebe1660bd840 100644
@@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_block *sb)
 	return 0;
 }
 
+/*
+ * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * @sb: super block
+ * TODO: Later add support for bigalloc
+ */
+static void ext4_atomic_write_init(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+
+	if (!bdev_can_atomic_write(bdev))
+		return;
+
+	if (!ext4_has_feature_extents(sb))
+		return;
+
+	sbi->s_awu_min = max(sb->s_blocksize,
+			      bdev_atomic_write_unit_min_bytes(bdev));
+	sbi->s_awu_max = min(sb->s_blocksize,
+			      bdev_atomic_write_unit_max_bytes(bdev));
+	if (sbi->s_awu_min && sbi->s_awu_max &&
+	    sbi->s_awu_min <= 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 = 0;
+		sbi->s_awu_max = 0;
+	}
+}
+
 static void ext4_fast_commit_init(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
 	spin_lock_init(&sbi->s_bdev_wb_lock);
 
+	ext4_atomic_write_init(sb);
 	ext4_fast_commit_init(sb);
 
 	sb->s_root = NULL;

Signature · 1 line

2.46.0

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Darrick J. Wong

Reviewed-by on v4 4/4

2024-11-01 14:46 UTC #12 lore raw

Re: [PATCH v4 4/4] ext4: Do not fallback to buffered-io for DIO atomic write

In reply to Ritesh Harjani (IBM)

Quoted 9 lines · Ritesh Harjani (IBM)

atomic writes is currently only supported for single fsblock and only for direct-io. We should not return -ENOTBLK for atomic writes since we want the atomic write request to either complete fully or fail otherwise. Hence, we should never fallback to buffered-io in case of DIO atomic write requests.
Let's also catch if this ever happens by adding some WARN_ON_ONCE before buffered-io handling for direct-io atomic writes. More details of the discussion [1].

Quoted 7 lines

While at it let's add an inline helper ext4_want_directio_fallback() which simplifies the logic checks and inherently fixes condition on when to return -ENOTBLK which otherwise was always returning true for any write or directio in ext4_iomap_end(). It was ok since ext4 only supports direct-io via iomap.
[1]: https://lore.kernel.org/linux-xfs/[email protected]/T/#m9dbecc11bed713ed0d7a486432c56b105b555f04
Suggested-by Darrick J. Wong <[email protected]> # inline helper

Looks good to me now,

Reviewed-by Darrick J. Wong <[email protected]>

--D

Quoted 72 lines

Signed-off-by Ritesh Harjani (IBM) <[email protected]>

---
 fs/ext4/file.c  |  7 +++++++
 fs/ext4/inode.c | 27 ++++++++++++++++++++++-----
 2 files changed, 29 insertions(+), 5 deletions(-)

fs/ext4/file.c +7 -0

index 96d936f5584b..a7de03e47db0 100644
@@ -599,6 +599,13 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		ssize_t err;
 		loff_t endbyte;
 
+		/*
+		 * There is no support for atomic writes on buffered-io yet,
+		 * we should never fallback to buffered-io for DIO atomic
+		 * writes.
+		 */
+		WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC);
+
 		offset = iocb->ki_pos;
 		err = ext4_buffered_write_iter(iocb, from);
 		if (err < 0)

fs/ext4/inode.c +22 -6

index 3e827cfa762e..5b9eeb74ce47 100644
@@ -3444,17 +3444,34 @@ static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset,
 	return ret;
 }
 
+static inline bool ext4_want_directio_fallback(unsigned flags, ssize_t written)
+{
+	/* must be a directio to fall back to buffered */
+	if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) !=
+		    (IOMAP_WRITE | IOMAP_DIRECT))
+		return false;
+
+	/* atomic writes are all-or-nothing */
+	if (flags & IOMAP_ATOMIC)
+		return false;
+
+	/* can only try again if we wrote nothing */
+	return written == 0;
+}
+
 static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
 			  ssize_t written, unsigned flags, struct iomap *iomap)
 {
 	/*
 	 * Check to see whether an error occurred while writing out the data to
-	 * the allocated blocks. If so, return the magic error code so that we
-	 * fallback to buffered I/O and attempt to complete the remainder of
-	 * the I/O. Any blocks that may have been allocated in preparation for
-	 * the direct I/O will be reused during buffered I/O.
+	 * the allocated blocks. If so, return the magic error code for
+	 * non-atomic write so that we fallback to buffered I/O and attempt to
+	 * complete the remainder of the I/O.
+	 * For non-atomic writes, any blocks that may have been
+	 * allocated in preparation for the direct I/O will be reused during
+	 * buffered I/O. For atomic write, we never fallback to buffered-io.
 	 */
-	if (flags & (IOMAP_WRITE | IOMAP_DIRECT) && written == 0)
+	if (ext4_want_directio_fallback(flags, written))
 		return -ENOTBLK;
 
 	return 0;
--

2.46.0

Darrick J. Wong

Reviewed-by on v4 1/4

2024-11-01 15:12 UTC #3 lore raw

Re: [PATCH v4 1/4] ext4: Add statx support for atomic writes

In reply to Ritesh Harjani (IBM)

Quoted 8 lines · Ritesh Harjani (IBM)

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 <[email protected]>
Signed-off-by Ojaswin Mujoo <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

Looks good to me,

Reviewed-by Darrick J. Wong <[email protected]>

--D

Quoted 110 lines

---
 fs/ext4/ext4.h  | 10 ++++++++++
 fs/ext4/inode.c | 12 ++++++++++++
 fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

fs/ext4/ext4.h +10 -0

index 44b0d418143c..494d443e9fc9 100644
@@ -1729,6 +1729,10 @@ struct ext4_sb_info {
 	 */
 	struct work_struct s_sb_upd_work;
 
+	/* 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;

@@ -3855,6 +3859,12 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
 	return buffer_uptodate(bh);
 }
 
+static inline bool ext4_inode_can_atomic_write(struct inode *inode)
+{
+
+	return S_ISREG(inode->i_mode) && EXT4_SB(inode->i_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);

fs/ext4/inode.c +12 -0

index 54bdd4884fe6..3e827cfa762e 100644
@@ -5578,6 +5578,18 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
 		}
 	}
 
+	if ((request_mask & STATX_WRITE_ATOMIC) && S_ISREG(inode->i_mode)) {
+		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+		unsigned int awu_min = 0, awu_max = 0;
+
+		if (ext4_inode_can_atomic_write(inode)) {
+			awu_min = sbi->s_awu_min;
+			awu_max = sbi->s_awu_max;
+		}
+
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+	}
+
 	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
 	if (flags & EXT4_APPEND_FL)
 		stat->attributes |= STATX_ATTR_APPEND;

fs/ext4/super.c +31 -0

index 16a4ce704460..ebe1660bd840 100644
@@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_block *sb)
 	return 0;
 }
 
+/*
+ * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * @sb: super block
+ * TODO: Later add support for bigalloc
+ */
+static void ext4_atomic_write_init(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+
+	if (!bdev_can_atomic_write(bdev))
+		return;
+
+	if (!ext4_has_feature_extents(sb))
+		return;
+
+	sbi->s_awu_min = max(sb->s_blocksize,
+			      bdev_atomic_write_unit_min_bytes(bdev));
+	sbi->s_awu_max = min(sb->s_blocksize,
+			      bdev_atomic_write_unit_max_bytes(bdev));
+	if (sbi->s_awu_min && sbi->s_awu_max &&
+	    sbi->s_awu_min <= 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 = 0;
+		sbi->s_awu_max = 0;
+	}
+}
+
 static void ext4_fast_commit_init(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
 	spin_lock_init(&sbi->s_bdev_wb_lock);
 
+	ext4_atomic_write_init(sb);
 	ext4_fast_commit_init(sb);
 
 	sb->s_root = NULL;

Signature · 1 line

2.46.0

John Garry

Reviewed-by on v4 1/4

2024-11-01 16:01 UTC #4 lore raw

Re: [PATCH v4 1/4] ext4: Add statx support for atomic writes

In reply to Ritesh Harjani (IBM)

Quoted 8 lines · Ritesh Harjani (IBM)

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 <[email protected]>
Signed-off-by Ojaswin Mujoo <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>

Regardless of nitpicks:

Reviewed-by John Garry <[email protected]>

Quoted 22 lines

---
  fs/ext4/ext4.h  | 10 ++++++++++
  fs/ext4/inode.c | 12 ++++++++++++
  fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
  3 files changed, 53 insertions(+)

fs/ext4/ext4.h +4 -0

index 44b0d418143c..494d443e9fc9 100644
@@ -1729,6 +1729,10 @@ struct ext4_sb_info {
  	 */
  	struct work_struct s_sb_upd_work;
 
+	/* 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;

fs/ext4/ext4.h static inline int ext4_buffer_uptodate(struct buffer_head *bh) · line 3864

Quoted 6 lines

fs/ext4/ext4.h +3 -0

@@ -3855,6 +3859,12 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
  	return buffer_uptodate(bh);
  }
 
+static inline bool ext4_inode_can_atomic_write(struct inode *inode)
+{
+

nit: superfluous blank line

fs/ext4/ext4.h static inline int ext4_buffer_uptodate(struct buffer_head *bh) · line 3865

Quoted 1 line

fs/ext4/ext4.h +1 -0

+	return S_ISREG(inode->i_mode) && EXT4_SB(inode->i_sb)->s_awu_min > 0;

I am not sure if the S_ISREG() check is required. Other callers also do the check (like ext4_getattr() for when calling ext4_inode_can_atomic_write()) or don't need it (ext4_file_open()). I say ext4_file_open() doesn't need it as ext4_file_open() is only ever called for regular files, right?

Quoted 10 lines

fs/ext4/ext4.h +2 -0

+}
+
  extern int ext4_block_write_begin(handle_t *handle, struct folio *folio,
  				  loff_t pos, unsigned len,
  				  get_block_t *get_block);

fs/ext4/inode.c +0 -0

index 54bdd4884fe6..3e827cfa762e 100644

fs/ext4/inode.c int ext4_getattr(struct mnt_idmap *idmap, const struct path *path, · line 5581

Quoted 4 lines

fs/ext4/inode.c +1 -0

@@ -5578,6 +5578,18 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
  		}
  	}
 
+	if ((request_mask & STATX_WRITE_ATOMIC) && S_ISREG(inode->i_mode)) {

nit: maybe you could have factored out the S_ISREG() check with STATX_DIOALIGN

Quoted 63 lines

fs/ext4/inode.c +11 -0

+		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+		unsigned int awu_min = 0, awu_max = 0;
+
+		if (ext4_inode_can_atomic_write(inode)) {
+			awu_min = sbi->s_awu_min;
+			awu_max = sbi->s_awu_max;
+		}
+
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+	}
+
  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
  	if (flags & EXT4_APPEND_FL)
  		stat->attributes |= STATX_ATTR_APPEND;

fs/ext4/super.c +31 -0

index 16a4ce704460..ebe1660bd840 100644
@@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_block *sb)
  	return 0;
  }
 
+/*
+ * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * @sb: super block
+ * TODO: Later add support for bigalloc
+ */
+static void ext4_atomic_write_init(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+
+	if (!bdev_can_atomic_write(bdev))
+		return;
+
+	if (!ext4_has_feature_extents(sb))
+		return;
+
+	sbi->s_awu_min = max(sb->s_blocksize,
+			      bdev_atomic_write_unit_min_bytes(bdev));
+	sbi->s_awu_max = min(sb->s_blocksize,
+			      bdev_atomic_write_unit_max_bytes(bdev));
+	if (sbi->s_awu_min && sbi->s_awu_max &&
+	    sbi->s_awu_min <= 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 = 0;
+		sbi->s_awu_max = 0;
+	}
+}
+
  static void ext4_fast_commit_init(struct super_block *sb)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
  	spin_lock_init(&sbi->s_bdev_wb_lock);
 
+	ext4_atomic_write_init(sb);
  	ext4_fast_commit_init(sb);
 
  	sb->s_root = NULL;

Ritesh Harjani (IBM)

author reviewer

2024-11-01 18:02 UTC #5 lore raw

Re: [PATCH v4 1/4] ext4: Add statx support for atomic writes

Quoted 6 lines · John Garry

Quoted 5 lines · Ritesh Harjani (IBM)
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.

Quoted 8 lines

Quoted 3 lines
Co-developed-by Ojaswin Mujoo <[email protected]>
Signed-off-by Ojaswin Mujoo <[email protected]>
Signed-off-by Ritesh Harjani (IBM) <[email protected]>
Regardless of nitpicks:
Reviewed-by John Garry <[email protected]>

Thanks John for the review!

Since as you too mentioned the remaining points are minor and not critical review comments, I will address them next time in the multi-fsblock variant. With all other aspects now finalized in this v4 version, this looks ready to be picked up for the merge window.

-ritesh

Quoted 25 lines

---
  fs/ext4/ext4.h  | 10 ++++++++++
  fs/ext4/inode.c | 12 ++++++++++++
  fs/ext4/super.c | 31 +++++++++++++++++++++++++++++++
  3 files changed, 53 insertions(+)

fs/ext4/ext4.h +4 -0

index 44b0d418143c..494d443e9fc9 100644
@@ -1729,6 +1729,10 @@ struct ext4_sb_info {
  	 */
  	struct work_struct s_sb_upd_work;
 
+	/* 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;

@@ -3855,6 +3859,12 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
  	return buffer_uptodate(bh);
  }

Quoted 6 lines

fs/ext4/ext4.h static inline int ext4_buffer_uptodate(struct buffer_head *bh) · line 3864
Quoted 3 lines
fs/ext4/ext4.h +3 -0
+static inline bool ext4_inode_can_atomic_write(struct inode *inode)
+{
+
nit: superfluous blank line

Sure.

Quoted 8 lines

fs/ext4/ext4.h static inline int ext4_buffer_uptodate(struct buffer_head *bh) · line 3865
Quoted 1 line
fs/ext4/ext4.h +1 -0
+	return S_ISREG(inode->i_mode) && EXT4_SB(inode->i_sb)->s_awu_min > 0;
I am not sure if the S_ISREG() check is required. Other callers also do the check (like ext4_getattr() for when calling ext4_inode_can_atomic_write()) or don't need it (ext4_file_open()). I say ext4_file_open() doesn't need it as ext4_file_open() is only ever called for regular files, right?

Yes. However I believe we might end up using this from other places when we add support of extsize. So we might need S_ISREG check. But sure let me re-think on that during the multi-fsblock variant time.

Quoted 13 lines

fs/ext4/ext4.h +2 -0

+}
+
  extern int ext4_block_write_begin(handle_t *handle, struct folio *folio,
  				  loff_t pos, unsigned len,
  				  get_block_t *get_block);

fs/ext4/inode.c +0 -0

index 54bdd4884fe6..3e827cfa762e 100644
@@ -5578,6 +5578,18 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
  		}
  	}

Quoted 5 lines

fs/ext4/inode.c int ext4_getattr(struct mnt_idmap *idmap, const struct path *path, · line 5581
Quoted 1 line
fs/ext4/inode.c +1 -0
+	if ((request_mask & STATX_WRITE_ATOMIC) && S_ISREG(inode->i_mode)) {
nit: maybe you could have factored out the S_ISREG() check with STATX_DIOALIGN

Sure.

Quoted 63 lines

fs/ext4/inode.c +11 -0

+		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+		unsigned int awu_min = 0, awu_max = 0;
+
+		if (ext4_inode_can_atomic_write(inode)) {
+			awu_min = sbi->s_awu_min;
+			awu_max = sbi->s_awu_max;
+		}
+
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+	}
+
  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
  	if (flags & EXT4_APPEND_FL)
  		stat->attributes |= STATX_ATTR_APPEND;

fs/ext4/super.c +31 -0

index 16a4ce704460..ebe1660bd840 100644
@@ -4425,6 +4425,36 @@ static int ext4_handle_clustersize(struct super_block *sb)
  	return 0;
  }
 
+/*
+ * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * @sb: super block
+ * TODO: Later add support for bigalloc
+ */
+static void ext4_atomic_write_init(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+
+	if (!bdev_can_atomic_write(bdev))
+		return;
+
+	if (!ext4_has_feature_extents(sb))
+		return;
+
+	sbi->s_awu_min = max(sb->s_blocksize,
+			      bdev_atomic_write_unit_min_bytes(bdev));
+	sbi->s_awu_max = min(sb->s_blocksize,
+			      bdev_atomic_write_unit_max_bytes(bdev));
+	if (sbi->s_awu_min && sbi->s_awu_max &&
+	    sbi->s_awu_min <= 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 = 0;
+		sbi->s_awu_max = 0;
+	}
+}
+
  static void ext4_fast_commit_init(struct super_block *sb)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

@@ -5336,6 +5366,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
  	spin_lock_init(&sbi->s_bdev_wb_lock);
 
+	ext4_atomic_write_init(sb);
  	ext4_fast_commit_init(sb);
 
  	sb->s_root = NULL;

kernel test robot

build bot

2024-11-02 10:16 UTC #13 lore raw

Re: [PATCH v4 4/4] ext4: Do not fallback to buffered-io for DIO atomic write

In reply to Ritesh Harjani (IBM)

kernel test robot noticed the following build errors:

Hi Ritesh,

kernel test robot noticed the following build errors:

[auto build test ERROR on tytso-ext4/dev]
[also build test ERROR on linus/master v6.12-rc5 next-20241101] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ritesh-Harjani-IBM/ext4-Add-statx-support-for-atomic-writes/20241101-145608
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
patch link:    https://lore.kernel.org/r/78fb5c40dde4847dc32af09e668a6f81fa251137.1730437365.git.ritesh.list%40gmail.com
patch subject: [PATCH v4 4/4] ext4: Do not fallback to buffered-io for DIO atomic write
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20241102/[email protected]/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241102/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All errors (new ones prefixed by >>):

In file included from fs/ext4/inode.c:26:
In file included from include/linux/pagemap.h:8:
In file included from include/linux/mm.h:2213:
include/linux/vmstat.h:504:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]

     504 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     505 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:511:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     511 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     512 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:524:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     524 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     525 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
>> fs/ext4/inode.c:3455:14: error: use of undeclared identifier 'IOMAP_ATOMIC'

3455 | if (flags & IOMAP_ATOMIC)
| ^
4 warnings and 1 error generated.

vim +/IOMAP_ATOMIC +3455 fs/ext4/inode.c

3446
3447 static inline bool ext4_want_directio_fallback(unsigned flags, ssize_t written)
3448 {
3449 /* must be a directio to fall back to buffered */
3450 if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) !=
3451 (IOMAP_WRITE | IOMAP_DIRECT))
3452 return false;
3453
3454 /* atomic writes are all-or-nothing */

> 3455		if (flags & IOMAP_ATOMIC)

3456 return false;
3457
3458 /* can only try again if we wrote nothing */
3459 return written == 0;
3460 }
3461

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