[PATCH v6.1 6/7] fs/xfs: Handle CoW for fsdax write() path

From: Shiyang Ruan
Date: Tue Jun 15 2021 - 03:22:08 EST

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In reply to: ruansy.fnst@xxxxxxxxxxx: "RE: [PATCH v6 6/7] fs/xfs: Handle CoW for fsdax write() path"
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Hi Darrick,

Since other patches looks good, I post this RFC patch singly to hot-fix the
problem in xfs_dax_write_iomap_ops->iomap_end() of v6 that the error code was
ingored. I will split this in two patches(changes in iomap and xfs
respectively) in next formal version if it looks ok.

====

Introduce a new interface called "iomap_post_actor()" in iomap_ops. And call it
between ->actor() and ->iomap_end(). It is mean to handle the error code
returned from ->actor(). In this patchset, it is used to remap or cancel the
CoW extents according to the error code.

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
fs/dax.c | 27 ++++++++++++++++++---------
fs/iomap/apply.c | 4 ++++
fs/xfs/xfs_bmap_util.c | 3 +--
fs/xfs/xfs_file.c | 5 +++--
fs/xfs/xfs_iomap.c | 33 ++++++++++++++++++++++++++++++++-
fs/xfs/xfs_iomap.h | 24 ++++++++++++++++++++++++
fs/xfs/xfs_iops.c | 7 +++----
fs/xfs/xfs_reflink.c | 3 +--
include/linux/iomap.h | 8 ++++++++
9 files changed, 94 insertions(+), 20 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 93f16210847b..0740c2610b6f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1537,7 +1537,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
struct iomap iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
unsigned flags = IOMAP_FAULT;
- int error;
+ int error, copied = PAGE_SIZE;
bool write = vmf->flags & FAULT_FLAG_WRITE;
vm_fault_t ret = 0, major = 0;
void *entry;
@@ -1598,7 +1598,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
ret = dax_fault_actor(vmf, pfnp, &xas, &entry, false, flags,
&iomap, &srcmap);
if (ret == VM_FAULT_SIGBUS)
- goto finish_iomap;
+ goto finish_iomap_actor;

/* read/write MAPPED, CoW UNWRITTEN */
if (iomap.flags & IOMAP_F_NEW) {
@@ -1607,10 +1607,16 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
major = VM_FAULT_MAJOR;
}

+ finish_iomap_actor:
+ if (ops->iomap_post_actor) {
+ if (ret & VM_FAULT_ERROR)
+ copied = 0;
+ ops->iomap_post_actor(inode, pos, PMD_SIZE, copied, flags,
+ &iomap, &srcmap);
+ }
+
finish_iomap:
if (ops->iomap_end) {
- int copied = PAGE_SIZE;
-
if (ret & VM_FAULT_ERROR)
copied = 0;
/*
@@ -1677,7 +1683,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
pgoff_t max_pgoff;
void *entry;
loff_t pos;
- int error;
+ int error, copied = PMD_SIZE;

/*
* Check whether offset isn't beyond end of file now. Caller is
@@ -1736,12 +1742,15 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
ret = dax_fault_actor(vmf, pfnp, &xas, &entry, true, flags,
&iomap, &srcmap);

+ if (ret == VM_FAULT_FALLBACK)
+ copied = 0;
+ if (ops->iomap_post_actor) {
+ ops->iomap_post_actor(inode, pos, PMD_SIZE, copied, flags,
+ &iomap, &srcmap);
+ }
+
finish_iomap:
if (ops->iomap_end) {
- int copied = PMD_SIZE;
-
- if (ret == VM_FAULT_FALLBACK)
- copied = 0;
/*
* The fault is done by now and there's no way back (other
* thread may be already happily using PMD we have installed).
diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
index 0493da5286ad..26a54ded184f 100644
--- a/fs/iomap/apply.c
+++ b/fs/iomap/apply.c
@@ -84,6 +84,10 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
written = actor(inode, pos, length, data, &iomap,
srcmap.type != IOMAP_HOLE ? &srcmap : &iomap);

+ if (ops->iomap_post_actor) {
+ written = ops->iomap_post_actor(inode, pos, length, written,
+ flags, &iomap, &srcmap);
+ }
out:
/*
* Now the data has been copied, commit the range we've copied. This
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index a5e9d7d34023..2a36dc93ff27 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -965,8 +965,7 @@ xfs_free_file_space(
return 0;
if (offset + len > XFS_ISIZE(ip))
len = XFS_ISIZE(ip) - offset;
- error = iomap_zero_range(VFS_I(ip), offset, len, NULL,
- &xfs_buffered_write_iomap_ops);
+ error = xfs_iomap_zero_range(ip, offset, len, NULL);
if (error)
return error;

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 396ef36dcd0a..89406ec6741b 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -684,11 +684,12 @@ xfs_file_dax_write(
pos = iocb->ki_pos;

trace_xfs_file_dax_write(iocb, from);
- ret = dax_iomap_rw(iocb, from, &xfs_direct_write_iomap_ops);
+ ret = dax_iomap_rw(iocb, from, &xfs_dax_write_iomap_ops);
if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
i_size_write(inode, iocb->ki_pos);
error = xfs_setfilesize(ip, pos, ret);
}
+
out:
if (iolock)
xfs_iunlock(ip, iolock);
@@ -1309,7 +1310,7 @@ __xfs_filemap_fault(

ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
(write_fault && !vmf->cow_page) ?
- &xfs_direct_write_iomap_ops :
+ &xfs_dax_write_iomap_ops :
&xfs_read_iomap_ops);
if (ret & VM_FAULT_NEEDDSYNC)
ret = dax_finish_sync_fault(vmf, pe_size, pfn);
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index d154f42e2dc6..2f322e2f8544 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -761,7 +761,8 @@ xfs_direct_write_iomap_begin(

/* may drop and re-acquire the ilock */
error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
- &lockmode, flags & IOMAP_DIRECT);
+ &lockmode,
+ (flags & IOMAP_DIRECT) || IS_DAX(inode));
if (error)
goto out_unlock;
if (shared)
@@ -854,6 +855,36 @@ const struct iomap_ops xfs_direct_write_iomap_ops = {
.iomap_begin = xfs_direct_write_iomap_begin,
};

+static int
+xfs_dax_write_iomap_post_actor(
+ struct inode *inode,
+ loff_t pos,
+ loff_t length,
+ ssize_t written,
+ unsigned int flags,
+ struct iomap *iomap,
+ struct iomap *srcmap)
+{
+ int error = 0;
+ struct xfs_inode *ip = XFS_I(inode);
+ bool cow = xfs_is_cow_inode(ip);
+
+ if (written <= 0) {
+ if (cow)
+ xfs_reflink_cancel_cow_range(ip, pos, length, true);
+ return written;
+ }
+
+ if (cow)
+ error = xfs_reflink_end_cow(ip, pos, written);
+ return error ?: written;
+}
+
+const struct iomap_ops xfs_dax_write_iomap_ops = {
+ .iomap_begin = xfs_direct_write_iomap_begin,
+ .iomap_post_actor = xfs_dax_write_iomap_post_actor,
+};
+
static int
xfs_buffered_write_iomap_begin(
struct inode *inode,
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index 7d3703556d0e..fbacf638ab21 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -42,8 +42,32 @@ xfs_aligned_fsb_count(

extern const struct iomap_ops xfs_buffered_write_iomap_ops;
extern const struct iomap_ops xfs_direct_write_iomap_ops;
+extern const struct iomap_ops xfs_dax_write_iomap_ops;
extern const struct iomap_ops xfs_read_iomap_ops;
extern const struct iomap_ops xfs_seek_iomap_ops;
extern const struct iomap_ops xfs_xattr_iomap_ops;

+static inline int
+xfs_iomap_zero_range(
+ struct xfs_inode *ip,
+ loff_t offset,
+ loff_t len,
+ bool *did_zero)
+{
+ return iomap_zero_range(VFS_I(ip), offset, len, did_zero,
+ IS_DAX(VFS_I(ip)) ? &xfs_dax_write_iomap_ops
+ : &xfs_buffered_write_iomap_ops);
+}
+
+static inline int
+xfs_iomap_truncate_page(
+ struct xfs_inode *ip,
+ loff_t pos,
+ bool *did_zero)
+{
+ return iomap_truncate_page(VFS_I(ip), pos, did_zero,
+ IS_DAX(VFS_I(ip)) ? &xfs_dax_write_iomap_ops
+ : &xfs_buffered_write_iomap_ops);
+}
+
#endif /* __XFS_IOMAP_H__*/
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index dfe24b7f26e5..6d936c3e1a6e 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -911,8 +911,8 @@ xfs_setattr_size(
*/
if (newsize > oldsize) {
trace_xfs_zero_eof(ip, oldsize, newsize - oldsize);
- error = iomap_zero_range(inode, oldsize, newsize - oldsize,
- &did_zeroing, &xfs_buffered_write_iomap_ops);
+ error = xfs_iomap_zero_range(ip, oldsize, newsize - oldsize,
+ &did_zeroing);
} else {
/*
* iomap won't detect a dirty page over an unwritten block (or a
@@ -924,8 +924,7 @@ xfs_setattr_size(
newsize);
if (error)
return error;
- error = iomap_truncate_page(inode, newsize, &did_zeroing,
- &xfs_buffered_write_iomap_ops);
+ error = xfs_iomap_truncate_page(ip, newsize, &did_zeroing);
}

if (error)
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index d25434f93235..9a780948dbd0 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1266,8 +1266,7 @@ xfs_reflink_zero_posteof(
return 0;

trace_xfs_zero_eof(ip, isize, pos - isize);
- return iomap_zero_range(VFS_I(ip), isize, pos - isize, NULL,
- &xfs_buffered_write_iomap_ops);
+ return xfs_iomap_zero_range(ip, isize, pos - isize, NULL);
}

/*
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 95562f863ad0..58f2e1c78018 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -135,6 +135,14 @@ struct iomap_ops {
unsigned flags, struct iomap *iomap,
struct iomap *srcmap);

+ /*
+ * Handle the error code from actor(). Do the finishing jobs for extra
+ * operations, such as CoW, according to whether written is negative.
+ */
+ int (*iomap_post_actor)(struct inode *inode, loff_t pos, loff_t length,
+ ssize_t written, unsigned flags, struct iomap *iomap,
+ struct iomap *srcmap);
+
/*
* Commit and/or unreserve space previous allocated using iomap_begin.
* Written indicates the length of the successful write operation which
--
2.31.1

Next message: Jens Wiklander: "Re: [PATCH v5 0/8] tee: Improve support for kexec and kdump"
Previous message: Christoph Hellwig: "Re: [PATCH 5/7] signal: Add unsafe_copy_siginfo_to_user()"
In reply to: ruansy.fnst@xxxxxxxxxxx: "RE: [PATCH v6 6/7] fs/xfs: Handle CoW for fsdax write() path"
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