Messages in this thread | | | Date | Mon, 26 Feb 2024 09:07:21 +0000 | Subject | Re: [PATCH v4 04/11] fs: Add initial atomic write support info to statx | From | John Garry <> |
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On 24/02/2024 18:46, Ritesh Harjani (IBM) wrote: > John Garry <john.g.garry@oracle.com> writes: > >> From: Prasad Singamsetty <prasad.singamsetty@oracle.com> >> >> 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. >> >> Signed-off-by: Prasad Singamsetty <prasad.singamsetty@oracle.com> >> #jpg: relocate bdev support to another patch > > ^^^ miss maybe? >> Signed-off-by: John Garry <john.g.garry@oracle.com> >> --- >> fs/stat.c | 34 ++++++++++++++++++++++++++++++++++ >> include/linux/fs.h | 3 +++ >> include/linux/stat.h | 3 +++ >> include/uapi/linux/stat.h | 9 ++++++++- >> 4 files changed, 48 insertions(+), 1 deletion(-) >> >> diff --git a/fs/stat.c b/fs/stat.c >> index 77cdc69eb422..522787a4ab6a 100644 >> --- 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 the atomic writes statx attributes >> + * @stat: Where to fill in the attribute flags >> + * @unit_min: Minimum supported atomic write length > + * @unit_min: Minimum supported atomic write length in bytes > > >> + * @unit_max: Maximum supported atomic write length > + * @unit_max: Maximum supported atomic write length in bytes > > mentioning unit of the length might be useful here.
Yeah, I have already improved this as suggested.
> >> + * >> + * 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, > > This (unit_min) can still go above in the same line.
ok
> >> + 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; > > Please log info about this in commit message about where this limit came > from?
ok
> Is it since we only support ubuf (which IIUC, only supports 1 > segment)? Later when we will add support for iovec, this limit can be > lifted?
It's not that we only support ubuf, but rather we only support one segment and that gives a ubuf type iter.
This is all related to how can can guarantee a unit_max advertised to userspace can always be written atomically.
This is further mentioned in the block layer patch.
> >> + >> + /* Confirm atomic writes are actually supported */ >> + stat->attributes |= STATX_ATTR_WRITE_ATOMIC; >> + } >> +} >> +EXPORT_SYMBOL(generic_fill_statx_atomic_writes); >> + >> /** >> * vfs_getattr_nosec - getattr without security checks >> * @path: file to get attributes from >> @@ -658,6 +689,9 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) >> tmp.stx_mnt_id = stat->mnt_id; >> tmp.stx_dio_mem_align = stat->dio_mem_align; >> tmp.stx_dio_offset_align = stat->dio_offset_align; >> + 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 7271640fd600..531140a7e27a 100644 >> --- a/include/linux/fs.h >> +++ b/include/linux/fs.h >> @@ -3167,6 +3167,9 @@ 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); > > We can make 80 col. width even with unit_min in the same first line as of *stat.
ok, I can check this.
> > >> 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 52150570d37a..2c5e2b8c6559 100644 >> --- a/include/linux/stat.h >> +++ b/include/linux/stat.h >> @@ -53,6 +53,9 @@ struct kstat { >> u32 dio_mem_align; >> u32 dio_offset_align; >> u64 change_cookie; >> + 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 2f2ee82d5517..c0e8e10d1de6 100644 >> --- a/include/uapi/linux/stat.h >> +++ b/include/uapi/linux/stat.h >> @@ -127,7 +127,12 @@ struct statx { >> __u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */ >> __u32 stx_dio_offset_align; /* File offset alignment for direct I/O */ >> /* 0xa0 */ >> - __u64 __spare3[12]; /* Spare space for future expansion */ >> + __u32 stx_atomic_write_unit_min; >> + __u32 stx_atomic_write_unit_max; >> + __u32 stx_atomic_write_segments_max; > > Let's add one liner for each of these fields similar to how it was done > for others? > > /* Minimum supported atomic write length in bytes */ > /* Maximum supported atomic write length in bytes */ > /* Maximum no. of segments (iovecs?) supported for atomic write */
ok
> > >> + __u32 __spare1; >> + /* 0xb0 */ >> + __u64 __spare3[10]; /* Spare space for future expansion */ >> /* 0x100 */ >> }; >> >> @@ -155,6 +160,7 @@ struct statx { >> #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */ >> #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_WRITE_ATOMIC 0x00008000U /* Want/got atomic_write_* fields */ >> >> #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */ >> >> @@ -190,6 +196,7 @@ 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 */ >> -- >> 2.31.1
Thanks, John
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