Commit 0f9ca80f authored by Prasad Singamsetty's avatar Prasad Singamsetty Committed by Jens Axboe
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fs: Add initial atomic write support info to statx 



Extend statx system call to return additional info for atomic write support
support for a file.

Helper function generic_fill_statx_atomic_writes() can be used by FSes to
fill in the relevant statx fields. For now atomic_write_segments_max will
always be 1, otherwise some rules would need to be imposed on iovec length
and alignment, which we don't want now.

Signed-off-by: default avatarPrasad Singamsetty <prasad.singamsetty@oracle.com>
jpg: relocate bdev support to another patch
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarJohn Garry <john.g.garry@oracle.com>
Acked-by: default avatarDarrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20240620125359.2684798-5-john.g.garry@oracle.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c34fc6f2

fs/stat.c

+34 −0
Original line number Diff line number Diff line
@@ -89,6 +89,37 @@ void generic_fill_statx_attr(struct inode *inode, struct kstat *stat) 
}

EXPORT_SYMBOL(generic_fill_statx_attr);



/**

 * generic_fill_statx_atomic_writes - Fill in atomic writes statx attributes

 * @stat:	Where to fill in the attribute flags

 * @unit_min:	Minimum supported atomic write length in bytes

 * @unit_max:	Maximum supported atomic write length in bytes

 *

 * Fill in the STATX{_ATTR}_WRITE_ATOMIC flags in the kstat structure from

 * atomic write unit_min and unit_max values.

 */

void generic_fill_statx_atomic_writes(struct kstat *stat,

				      unsigned int unit_min,

				      unsigned int unit_max)

{

	/* Confirm that the request type is known */

	stat->result_mask |= STATX_WRITE_ATOMIC;



	/* Confirm that the file attribute type is known */

	stat->attributes_mask |= STATX_ATTR_WRITE_ATOMIC;



	if (unit_min) {

		stat->atomic_write_unit_min = unit_min;

		stat->atomic_write_unit_max = unit_max;

		/* Initially only allow 1x segment */

		stat->atomic_write_segments_max = 1;



		/* Confirm atomic writes are actually supported */

		stat->attributes |= STATX_ATTR_WRITE_ATOMIC;

	}

}

EXPORT_SYMBOL_GPL(generic_fill_statx_atomic_writes);



/**

 * vfs_getattr_nosec - getattr without security checks

 * @path: file to get attributes from
@@ -659,6 +690,9 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) 
	tmp.stx_dio_mem_align = stat->dio_mem_align;

	tmp.stx_dio_offset_align = stat->dio_offset_align;

	tmp.stx_subvol = stat->subvol;

	tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min;

	tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max;

	tmp.stx_atomic_write_segments_max = stat->atomic_write_segments_max;



	return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;

}

include/linux/fs.h

+3 −0
Original line number Diff line number Diff line
@@ -3235,6 +3235,9 @@ extern const struct inode_operations page_symlink_inode_operations; 
extern void kfree_link(void *);

void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);

void generic_fill_statx_attr(struct inode *inode, struct kstat *stat);

void generic_fill_statx_atomic_writes(struct kstat *stat,

				      unsigned int unit_min,

				      unsigned int unit_max);

extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);

extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);

void __inode_add_bytes(struct inode *inode, loff_t bytes);

include/linux/stat.h

+3 −0
Original line number Diff line number Diff line
@@ -54,6 +54,9 @@ struct kstat { 
	u32		dio_offset_align;

	u64		change_cookie;

	u64		subvol;

	u32		atomic_write_unit_min;

	u32		atomic_write_unit_max;

	u32		atomic_write_segments_max;

};



/* These definitions are internal to the kernel for now. Mainly used by nfsd. */

include/uapi/linux/stat.h

+10 −2
Original line number Diff line number Diff line
@@ -126,9 +126,15 @@ struct statx { 
	__u64	stx_mnt_id;

	__u32	stx_dio_mem_align;	/* Memory buffer alignment for direct I/O */

	__u32	stx_dio_offset_align;	/* File offset alignment for direct I/O */

	__u64	stx_subvol;	/* Subvolume identifier */

	/* 0xa0 */

	__u64	__spare3[11];	/* Spare space for future expansion */

	__u64	stx_subvol;	/* Subvolume identifier */

	__u32	stx_atomic_write_unit_min;	/* Min atomic write unit in bytes */

	__u32	stx_atomic_write_unit_max;	/* Max atomic write unit in bytes */

	/* 0xb0 */

	__u32   stx_atomic_write_segments_max;	/* Max atomic write segment count */

	__u32   __spare1[1];

	/* 0xb8 */

	__u64	__spare3[9];	/* Spare space for future expansion */

	/* 0x100 */

};
@@ -157,6 +163,7 @@ struct statx { 
#define STATX_DIOALIGN		0x00002000U	/* Want/got direct I/O alignment info */

#define STATX_MNT_ID_UNIQUE	0x00004000U	/* Want/got extended stx_mount_id */

#define STATX_SUBVOL		0x00008000U	/* Want/got stx_subvol */

#define STATX_WRITE_ATOMIC	0x00010000U	/* Want/got atomic_write_* fields */



#define STATX__RESERVED		0x80000000U	/* Reserved for future struct statx expansion */
@@ -192,6 +199,7 @@ struct statx { 
#define STATX_ATTR_MOUNT_ROOT		0x00002000 /* Root of a mount */

#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */

#define STATX_ATTR_DAX			0x00200000 /* File is currently in DAX state */

#define STATX_ATTR_WRITE_ATOMIC		0x00400000 /* File supports atomic write operations */





#endif /* _UAPI_LINUX_STAT_H */