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fsdax: switch the fault handlers to use iomap_iter
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Avoid the open coded calls to ->iomap_begin and ->iomap_end and call
iomap_iter instead.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Darrick J. Wong <[email protected]>
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Christoph Hellwig authored and Darrick J. Wong committed Aug 17, 2021
1 parent c243619 commit 65dd814
Showing 1 changed file with 75 additions and 118 deletions.
193 changes: 75 additions & 118 deletions fs/dax.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1010,7 +1010,7 @@ static sector_t dax_iomap_sector(const struct iomap *iomap, loff_t pos)
return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
}

static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
static int dax_iomap_pfn(const struct iomap *iomap, loff_t pos, size_t size,
pfn_t *pfnp)
{
const sector_t sector = dax_iomap_sector(iomap, pos);
Expand Down Expand Up @@ -1068,7 +1068,7 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,

#ifdef CONFIG_FS_DAX_PMD
static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
struct iomap *iomap, void **entry)
const struct iomap *iomap, void **entry)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
unsigned long pmd_addr = vmf->address & PMD_MASK;
Expand Down Expand Up @@ -1120,7 +1120,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
}
#else
static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
struct iomap *iomap, void **entry)
const struct iomap *iomap, void **entry)
{
return VM_FAULT_FALLBACK;
}
Expand Down Expand Up @@ -1309,7 +1309,7 @@ static vm_fault_t dax_fault_return(int error)
* flushed on write-faults (non-cow), but not read-faults.
*/
static bool dax_fault_is_synchronous(unsigned long flags,
struct vm_area_struct *vma, struct iomap *iomap)
struct vm_area_struct *vma, const struct iomap *iomap)
{
return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
&& (iomap->flags & IOMAP_F_DIRTY);
Expand All @@ -1329,22 +1329,22 @@ static vm_fault_t dax_fault_synchronous_pfnp(pfn_t *pfnp, pfn_t pfn)
return VM_FAULT_NEEDDSYNC;
}

static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf, struct iomap *iomap,
loff_t pos)
static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf,
const struct iomap_iter *iter)
{
sector_t sector = dax_iomap_sector(iomap, pos);
sector_t sector = dax_iomap_sector(&iter->iomap, iter->pos);
unsigned long vaddr = vmf->address;
vm_fault_t ret;
int error = 0;

switch (iomap->type) {
switch (iter->iomap.type) {
case IOMAP_HOLE:
case IOMAP_UNWRITTEN:
clear_user_highpage(vmf->cow_page, vaddr);
break;
case IOMAP_MAPPED:
error = copy_cow_page_dax(iomap->bdev, iomap->dax_dev, sector,
vmf->cow_page, vaddr);
error = copy_cow_page_dax(iter->iomap.bdev, iter->iomap.dax_dev,
sector, vmf->cow_page, vaddr);
break;
default:
WARN_ON_ONCE(1);
Expand All @@ -1363,29 +1363,31 @@ static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf, struct iomap *iomap,
}

/**
* dax_fault_actor - Common actor to handle pfn insertion in PTE/PMD fault.
* dax_fault_iter - Common actor to handle pfn insertion in PTE/PMD fault.
* @vmf: vm fault instance
* @iter: iomap iter
* @pfnp: pfn to be returned
* @xas: the dax mapping tree of a file
* @entry: an unlocked dax entry to be inserted
* @pmd: distinguish whether it is a pmd fault
* @flags: iomap flags
* @iomap: from iomap_begin()
* @srcmap: from iomap_begin(), not equal to iomap if it is a CoW
*/
static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
struct xa_state *xas, void **entry, bool pmd,
unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
const struct iomap_iter *iter, pfn_t *pfnp,
struct xa_state *xas, void **entry, bool pmd)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
const struct iomap *iomap = &iter->iomap;
size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
bool write = vmf->flags & FAULT_FLAG_WRITE;
bool sync = dax_fault_is_synchronous(flags, vmf->vma, iomap);
bool sync = dax_fault_is_synchronous(iter->flags, vmf->vma, iomap);
unsigned long entry_flags = pmd ? DAX_PMD : 0;
int err = 0;
pfn_t pfn;

if (!pmd && vmf->cow_page)
return dax_fault_cow_page(vmf, iter);

/* if we are reading UNWRITTEN and HOLE, return a hole. */
if (!write &&
(iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) {
Expand All @@ -1399,7 +1401,7 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
}

err = dax_iomap_pfn(iomap, pos, size, &pfn);
err = dax_iomap_pfn(&iter->iomap, pos, size, &pfn);
if (err)
return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);

Expand All @@ -1422,32 +1424,31 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
int *iomap_errp, const struct iomap_ops *ops)
{
struct vm_area_struct *vma = vmf->vma;
struct address_space *mapping = vma->vm_file->f_mapping;
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
struct inode *inode = mapping->host;
loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
struct iomap iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
unsigned flags = IOMAP_FAULT;
int error;
bool write = vmf->flags & FAULT_FLAG_WRITE;
vm_fault_t ret = 0, major = 0;
struct iomap_iter iter = {
.inode = mapping->host,
.pos = (loff_t)vmf->pgoff << PAGE_SHIFT,
.len = PAGE_SIZE,
.flags = IOMAP_FAULT,
};
vm_fault_t ret = 0;
void *entry;
int error;

trace_dax_pte_fault(inode, vmf, ret);
trace_dax_pte_fault(iter.inode, vmf, ret);
/*
* Check whether offset isn't beyond end of file now. Caller is supposed
* to hold locks serializing us with truncate / punch hole so this is
* a reliable test.
*/
if (pos >= i_size_read(inode)) {
if (iter.pos >= i_size_read(iter.inode)) {
ret = VM_FAULT_SIGBUS;
goto out;
}

if (write && !vmf->cow_page)
flags |= IOMAP_WRITE;
if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
iter.flags |= IOMAP_WRITE;

entry = grab_mapping_entry(&xas, mapping, 0);
if (xa_is_internal(entry)) {
Expand All @@ -1466,59 +1467,34 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
goto unlock_entry;
}

/*
* Note that we don't bother to use iomap_iter here: DAX required
* the file system block size to be equal the page size, which means
* that we never have to deal with more than a single extent here.
*/
error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap, &srcmap);
if (iomap_errp)
*iomap_errp = error;
if (error) {
ret = dax_fault_return(error);
goto unlock_entry;
}
if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
ret = VM_FAULT_SIGBUS; /* fs corruption? */
goto finish_iomap;
}

if (vmf->cow_page) {
ret = dax_fault_cow_page(vmf, &iomap, pos);
goto finish_iomap;
}
while ((error = iomap_iter(&iter, ops)) > 0) {
if (WARN_ON_ONCE(iomap_length(&iter) < PAGE_SIZE)) {
iter.processed = -EIO; /* fs corruption? */
continue;
}

ret = dax_fault_actor(vmf, pfnp, &xas, &entry, false, flags,
&iomap, &srcmap);
if (ret == VM_FAULT_SIGBUS)
goto finish_iomap;
ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, false);
if (ret != VM_FAULT_SIGBUS &&
(iter.iomap.flags & IOMAP_F_NEW)) {
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
ret |= VM_FAULT_MAJOR;
}

/* read/write MAPPED, CoW UNWRITTEN */
if (iomap.flags & IOMAP_F_NEW) {
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
major = VM_FAULT_MAJOR;
if (!(ret & VM_FAULT_ERROR))
iter.processed = PAGE_SIZE;
}

finish_iomap:
if (ops->iomap_end) {
int copied = PAGE_SIZE;
if (iomap_errp)
*iomap_errp = error;
if (!ret && error)
ret = dax_fault_return(error);

if (ret & VM_FAULT_ERROR)
copied = 0;
/*
* The fault is done by now and there's no way back (other
* thread may be already happily using PTE we have installed).
* Just ignore error from ->iomap_end since we cannot do much
* with it.
*/
ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
}
unlock_entry:
dax_unlock_entry(&xas, entry);
out:
trace_dax_pte_fault_done(inode, vmf, ret);
return ret | major;
trace_dax_pte_fault_done(iter.inode, vmf, ret);
return ret;
}

#ifdef CONFIG_FS_DAX_PMD
Expand Down Expand Up @@ -1558,28 +1534,29 @@ static bool dax_fault_check_fallback(struct vm_fault *vmf, struct xa_state *xas,
static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
const struct iomap_ops *ops)
{
struct vm_area_struct *vma = vmf->vma;
struct address_space *mapping = vma->vm_file->f_mapping;
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER);
bool write = vmf->flags & FAULT_FLAG_WRITE;
unsigned int flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
struct inode *inode = mapping->host;
struct iomap_iter iter = {
.inode = mapping->host,
.len = PMD_SIZE,
.flags = IOMAP_FAULT,
};
vm_fault_t ret = VM_FAULT_FALLBACK;
struct iomap iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
pgoff_t max_pgoff;
void *entry;
loff_t pos;
int error;

if (vmf->flags & FAULT_FLAG_WRITE)
iter.flags |= IOMAP_WRITE;

/*
* Check whether offset isn't beyond end of file now. Caller is
* supposed to hold locks serializing us with truncate / punch hole so
* this is a reliable test.
*/
max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
max_pgoff = DIV_ROUND_UP(i_size_read(iter.inode), PAGE_SIZE);

trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
trace_dax_pmd_fault(iter.inode, vmf, max_pgoff, 0);

if (xas.xa_index >= max_pgoff) {
ret = VM_FAULT_SIGBUS;
Expand Down Expand Up @@ -1613,45 +1590,25 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
goto unlock_entry;
}

/*
* Note that we don't use iomap_iter here. We aren't doing I/O, only
* setting up a mapping, so really we're using iomap_begin() as a way
* to look up our filesystem block.
*/
pos = (loff_t)xas.xa_index << PAGE_SHIFT;
error = ops->iomap_begin(inode, pos, PMD_SIZE, flags, &iomap, &srcmap);
if (error)
goto unlock_entry;

if (iomap.offset + iomap.length < pos + PMD_SIZE)
goto finish_iomap;
iter.pos = (loff_t)xas.xa_index << PAGE_SHIFT;
while ((error = iomap_iter(&iter, ops)) > 0) {
if (iomap_length(&iter) < PMD_SIZE)
continue; /* actually breaks out of the loop */

ret = dax_fault_actor(vmf, pfnp, &xas, &entry, true, 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).
* Just ignore error from ->iomap_end since we cannot do much
* with it.
*/
ops->iomap_end(inode, pos, PMD_SIZE, copied, flags, &iomap);
ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, true);
if (ret != VM_FAULT_FALLBACK)
iter.processed = PMD_SIZE;
}

unlock_entry:
dax_unlock_entry(&xas, entry);
fallback:
if (ret == VM_FAULT_FALLBACK) {
split_huge_pmd(vma, vmf->pmd, vmf->address);
split_huge_pmd(vmf->vma, vmf->pmd, vmf->address);
count_vm_event(THP_FAULT_FALLBACK);
}
out:
trace_dax_pmd_fault_done(inode, vmf, max_pgoff, ret);
trace_dax_pmd_fault_done(iter.inode, vmf, max_pgoff, ret);
return ret;
}
#else
Expand Down

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