From: Prasad Singamsetty prasad.singamsetty@oracle.com
maillist inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9VTE3 CVE: NA
Reference: https://lore.kernel.org/all/20240326133813.3224593-1-john.g.garry@oracle.com...
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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 prasad.singamsetty@oracle.com jpg: relocate bdev support to another patch Signed-off-by: John Garry john.g.garry@oracle.com Signed-off-by: Long Li leo.lilong@huawei.com --- fs/stat.c | 34 ++++++++++++++++++++++++++++++++++ include/linux/fs.h | 4 ++++ include/linux/stat.h | 3 +++ include/uapi/linux/stat.h | 10 +++++++++- 4 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/fs/stat.c b/fs/stat.c index a8bf565886a8..f37e801fee98 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -51,6 +51,37 @@ void generic_fillattr(struct inode *inode, struct kstat *stat) } EXPORT_SYMBOL(generic_fillattr);
+/** + * 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 @@ -569,6 +600,9 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) tmp.stx_dev_major = MAJOR(stat->dev); tmp.stx_dev_minor = MINOR(stat->dev); tmp.stx_mnt_id = stat->mnt_id; + 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 5e37ba855083..fac4c49f9365 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3251,6 +3251,10 @@ extern int page_symlink(struct inode *inode, const char *symname, int len); extern const struct inode_operations page_symlink_inode_operations; extern void kfree_link(void *); extern void generic_fillattr(struct inode *, struct kstat *); +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_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 fff27e603814..d266d2be6606 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -46,6 +46,9 @@ struct kstat { struct timespec64 btime; /* File creation time */ u64 blocks; u64 mnt_id; + u32 atomic_write_unit_min; + u32 atomic_write_unit_max; + u32 atomic_write_segments_max; };
#endif diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h index 1500a0f58041..5ecb22f064ba 100644 --- a/include/uapi/linux/stat.h +++ b/include/uapi/linux/stat.h @@ -126,7 +126,12 @@ struct statx { __u64 stx_mnt_id; __u64 __spare2; /* 0xa0 */ - __u64 __spare3[12]; /* Spare space for future expansion */ + __u32 stx_atomic_write_unit_min; /* Min atomic write unit in bytes */ + __u32 stx_atomic_write_unit_max; /* Max atomic write unit in bytes */ + __u32 stx_atomic_write_segments_max; /* Max atomic write segment count */ + __u32 __spare3[1]; + /* 0xb0 */ + __u64 __spare4[10]; /* Spare space for future expansion */ /* 0x100 */ };
@@ -152,6 +157,8 @@ struct statx { #define STATX_BASIC_STATS 0x000007ffU /* The stuff in the normal stat struct */ #define STATX_BTIME 0x00000800U /* Want/got stx_btime */ #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */ +#define STATX_WRITE_ATOMIC 0x00008000U /* Want/got atomic_write_* fields */ +
#define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */
@@ -187,6 +194,7 @@ 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 */