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: Prasad Singamsetty <[email protected]>
jpg: relocate bdev support to another patch
Reviewed-by: Darrick J. Wong <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Signed-off-by: John Garry <[email protected]>
Acked-by: Darrick J. Wong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

diff --git a/fs/stat.c b/fs/stat.c
index 70bd3e888cfa301be28acf5f6fa5a5b655549d2a..72d0e6357b91f160515576fb1147da5ec3fb8826 100644 (file)
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -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;
 }

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e049414bef7da6aeed7f58900d7ce9749c4193f5..db26b4a70c628bb8e65b4898886b0803549c330e 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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);

diff --git a/include/linux/stat.h b/include/linux/stat.h
index bf92441dbad2841993a8ef2db1dd2b8b70f2c919..3d900c86981c5b0ae92bb4e972ff36586093f59f 100644 (file)
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -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. */

diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 67626d53531664d0a65fbcf62585204e41588d88..887a2528644168a3f0f16752e6b21958a89e0bac 100644 (file)
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -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 */