On 02/02/2024 17:52, Darrick J. Wong wrote:
On Wed, Jan 24, 2024 at 02:26:42PM +0000, John Garry wrote:
Add initial support for FS_XFLAG_ATOMICWRITES in rtvol.
Current kernel support for atomic writes is based on HW support (for atomic
writes). As such, it is required to ensure extent alignment with
atomic_write_unit_max so that an atomic write can result in a single
HW-compliant IO operation.
rtvol already guarantees extent alignment, so initially add support there.
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_format.h | 8 ++++++--
fs/xfs/libxfs/xfs_sb.c | 2 ++
fs/xfs/xfs_inode.c | 22 ++++++++++++++++++++++
fs/xfs/xfs_inode.h | 7 +++++++
fs/xfs/xfs_ioctl.c | 19 +++++++++++++++++--
fs/xfs/xfs_mount.h | 2 ++
fs/xfs/xfs_super.c | 4 ++++
7 files changed, 60 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 382ab1e71c0b..79fb0d4adeda 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -353,11 +353,13 @@ xfs_sb_has_compat_feature(
#define XFS_SB_FEAT_RO_COMPAT_RMAPBT (1 << 1) /* reverse map btree */
#define XFS_SB_FEAT_RO_COMPAT_REFLINK (1 << 2) /* reflinked files */
#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT (1 << 3) /* inobt block counts */
+#define XFS_SB_FEAT_RO_COMPAT_ATOMICWRITES (1 << 29) /* aligned file data extents */
I thought FORCEALIGN was going to signal aligned file data extent
allocations being mandatory?
Right, I'll fix that comment
This flag (AFAICT) simply marks the inode as something that gets
FMODE_CAN_ATOMIC_WRITES, right?
Correct
#define XFS_SB_FEAT_RO_COMPAT_ALL \
(XFS_SB_FEAT_RO_COMPAT_FINOBT | \
XFS_SB_FEAT_RO_COMPAT_RMAPBT | \
XFS_SB_FEAT_RO_COMPAT_REFLINK| \
- XFS_SB_FEAT_RO_COMPAT_INOBTCNT)
+ XFS_SB_FEAT_RO_COMPAT_INOBTCNT | \
+ XFS_SB_FEAT_RO_COMPAT_ATOMICWRITES)
#define XFS_SB_FEAT_RO_COMPAT_UNKNOWN ~XFS_SB_FEAT_RO_COMPAT_ALL
static inline bool
xfs_sb_has_ro_compat_feature(
@@ -1085,16 +1087,18 @@ static inline void xfs_dinode_put_rdev(struct xfs_dinode *dip, xfs_dev_t rdev)
#define XFS_DIFLAG2_COWEXTSIZE_BIT 2 /* copy on write extent size hint */
#define XFS_DIFLAG2_BIGTIME_BIT 3 /* big timestamps */
#define XFS_DIFLAG2_NREXT64_BIT 4 /* large extent counters */
+#define XFS_DIFLAG2_ATOMICWRITES_BIT 6
Needs a comment here ("files flagged for atomic writes").
ok
Also not sure
why you skipped bit 5, though I'm guessing it's because the forcealign
series is/was using it?
Right, I'll fix that
#define XFS_DIFLAG2_DAX (1 << XFS_DIFLAG2_DAX_BIT)
#define XFS_DIFLAG2_REFLINK (1 << XFS_DIFLAG2_REFLINK_BIT)
#define XFS_DIFLAG2_COWEXTSIZE (1 << XFS_DIFLAG2_COWEXTSIZE_BIT)
#define XFS_DIFLAG2_BIGTIME (1 << XFS_DIFLAG2_BIGTIME_BIT)
#define XFS_DIFLAG2_NREXT64 (1 << XFS_DIFLAG2_NREXT64_BIT)
+#define XFS_DIFLAG2_ATOMICWRITES (1 << XFS_DIFLAG2_ATOMICWRITES_BIT)
#define XFS_DIFLAG2_ANY \
(XFS_DIFLAG2_DAX | XFS_DIFLAG2_REFLINK | XFS_DIFLAG2_COWEXTSIZE | \
- XFS_DIFLAG2_BIGTIME | XFS_DIFLAG2_NREXT64)
+ XFS_DIFLAG2_BIGTIME | XFS_DIFLAG2_NREXT64 | XFS_DIFLAG2_ATOMICWRITES)
static inline bool xfs_dinode_has_bigtime(const struct xfs_dinode *dip)
{
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 4a9e8588f4c9..28a98130a56d 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -163,6 +163,8 @@ xfs_sb_version_to_features(
features |= XFS_FEAT_REFLINK;
if (sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_INOBTCNT)
features |= XFS_FEAT_INOBTCNT;
+ if (sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_ATOMICWRITES)
+ features |= XFS_FEAT_ATOMICWRITES;
if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_FTYPE)
features |= XFS_FEAT_FTYPE;
if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_SPINODES)
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 1fd94958aa97..0b0f525fd043 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -65,6 +65,26 @@ xfs_get_extsz_hint(
return 0;
}
+/*
+ * helper function to extract extent size
How does that differ from xfs_get_extsz_hint?
The idea of this function is to return the guaranteed extent alignment,
and not just the hint
+ */
+xfs_extlen_t
+xfs_get_extsz(
+ struct xfs_inode *ip)
+{
+ /*
+ * No point in aligning allocations if we need to COW to actually
+ * write to them.
What does alwayscow have to do with untorn writes?
Nothing at the moment, so I'll remove this.
+ */
+ if (xfs_is_always_cow_inode(ip))
+ return 0;
+
+ if (XFS_IS_REALTIME_INODE(ip))
+ return ip->i_mount->m_sb.sb_rextsize;
+
+ return 1;
+}
Does this function exist to return the allocation unit for a given file?
https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/commit/?h=djwong-wtf&id=b8ddcef3df8da02ed2c4aacbed1d811e60372006
Yes, something like xfs_inode_alloc_unitsize() there.
What's the upstream status for that change? I see it mentioned in
linux-xfs lore and seems to be part of a mega patchset.
+
/*
* Helper function to extract CoW extent size hint from inode.
* Between the extent size hint and the CoW extent size hint, we
@@ -629,6 +649,8 @@ xfs_ip2xflags(
flags |= FS_XFLAG_DAX;
if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE)
flags |= FS_XFLAG_COWEXTSIZE;
+ if (ip->i_diflags2 & XFS_DIFLAG2_ATOMICWRITES)
+ flags |= FS_XFLAG_ATOMICWRITES;
}
if (xfs_inode_has_attr_fork(ip))
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 97f63bacd4c2..0e0a21d9d30f 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -305,6 +305,11 @@ static inline bool xfs_inode_has_large_extent_counts(struct xfs_inode *ip)
return ip->i_diflags2 & XFS_DIFLAG2_NREXT64;
}
+static inline bool xfs_inode_atomicwrites(struct xfs_inode *ip)
I think this predicate wants a verb in its name, the rest of them have
"is" or "has" somewhere:
"xfs_inode_has_atomicwrites"
ok, fine.
Note that I was copying xfs_inode_forcealign() in terms of naming.
+{
+ return ip->i_diflags2 & XFS_DIFLAG2_ATOMICWRITES;
+}
+
/*
* Return the buftarg used for data allocations on a given inode.
*/
@@ -542,7 +547,9 @@ void xfs_lock_two_inodes(struct xfs_inode *ip0, uint ip0_mode,
struct xfs_inode *ip1, uint ip1_mode);
xfs_extlen_t xfs_get_extsz_hint(struct xfs_inode *ip);
+xfs_extlen_t xfs_get_extsz(struct xfs_inode *ip);
xfs_extlen_t xfs_get_cowextsz_hint(struct xfs_inode *ip);
+xfs_extlen_t xfs_get_atomicwrites_size(struct xfs_inode *ip);
int xfs_init_new_inode(struct mnt_idmap *idmap, struct xfs_trans *tp,
struct xfs_inode *pip, xfs_ino_t ino, umode_t mode,
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index f02b6e558af5..c380a3055be7 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1110,6 +1110,8 @@ xfs_flags2diflags2(
di_flags2 |= XFS_DIFLAG2_DAX;
if (xflags & FS_XFLAG_COWEXTSIZE)
di_flags2 |= XFS_DIFLAG2_COWEXTSIZE;
+ if (xflags & FS_XFLAG_ATOMICWRITES)
+ di_flags2 |= XFS_DIFLAG2_ATOMICWRITES;
return di_flags2;
}
@@ -1122,10 +1124,12 @@ xfs_ioctl_setattr_xflags(
{
struct xfs_mount *mp = ip->i_mount;
bool rtflag = (fa->fsx_xflags & FS_XFLAG_REALTIME);
+ bool atomic_writes = fa->fsx_xflags & FS_XFLAG_ATOMICWRITES;
uint64_t i_flags2;
- if (rtflag != XFS_IS_REALTIME_INODE(ip)) {
- /* Can't change realtime flag if any extents are allocated. */
Please augment this comment ("Can't change realtime or atomicwrites
flags if any extents are allocated") instead of deleting it.
I wasn't supposed to delete that - will remedy.
This is
validation code, the requirements should be spelled out in English.
+
+ if (rtflag != XFS_IS_REALTIME_INODE(ip) ||
+ atomic_writes != xfs_inode_atomicwrites(ip)) {
if (ip->i_df.if_nextents || ip->i_delayed_blks)
return -EINVAL;
}
@@ -1146,6 +1150,17 @@ xfs_ioctl_setattr_xflags(
if (i_flags2 && !xfs_has_v3inodes(mp))
return -EINVAL;
+ if (atomic_writes) {
+ if (!xfs_has_atomicwrites(mp))
+ return -EINVAL;
+
+ if (!rtflag)
+ return -EINVAL;
+
+ if (!is_power_of_2(mp->m_sb.sb_rextsize))
+ return -EINVAL;
Shouldn't we check sb_rextsize w.r.t. the actual block device queue
limits here? I keep seeing similar validation logic open-coded
throughout both atomic write patchsets:
if (l < queue_atomic_write_unit_min_bytes())
/* fail */
if (l > queue_atomic_write_unit_max_bytes())
/* fail */
if (!is_power_of_2(l))
/* fail */
/* ok */
which really should be a common helper somewhere.
I think that it is a reasonable comment about duplication the atomic
writes checks for the bdev and iomap write paths - I can try to improve
that.
But the is_power_of_2(mp->m_sb.sb_rextsize) check is to ensure that the
extent size is suitable for enabling atomic writes. I don't see a point
in checking the bdev queue limits here.
/*
* Don't set atomic write if the allocation unit doesn't
* align with the device requirements.
*/
if (!bdev_validate_atomic_write(<target blockdev>,
XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize))
return -EINVAL;
Too bad we have to figure out the target blockdev and file allocation
unit based on the ioctl in-params and can't use the xfs_inode helpers
here.
I am not sure what bdev_validate_atomic_write() would even do. If
sb_rextsize exceeded the bdev atomic write unit max, then we just cap
reported atomic write unit max in statx to that which the bdev reports
and vice-versa.
And didn't we previously have a concern that it is possible to change
the geometry of the device? If so, not much point in this check.
Thanks,
John
