| Message ID | 20210226002030.653855-6-ruansy.fnst@fujitsu.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fsdax,xfs: Add reflink&dedupe support for fsdax | expand |
On Fri, Feb 26, 2021 at 08:20:25AM +0800, Shiyang Ruan wrote: > We replace the existing entry to the newly allocated one in case of CoW. > Also, we mark the entry as PAGECACHE_TAG_TOWRITE so writeback marks this > entry as writeprotected. This helps us snapshots so new write > pagefaults after snapshots trigger a CoW. > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> > --- > fs/dax.c | 37 ++++++++++++++++++++++++++----------- > 1 file changed, 26 insertions(+), 11 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 748dfb89fb41..ec4b733e0b59 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -722,6 +722,9 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d > return 0; > } > > +#define DAX_IF_DIRTY (1 << 0) > +#define DAX_IF_COW (1 << 1) > + > /* > * By this point grab_mapping_entry() has ensured that we have a locked entry > * of the appropriate size so we don't have to worry about downgrading PMDs to > @@ -729,16 +732,19 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d > * already in the tree, we will skip the insertion and just dirty the PMD as > * appropriate. > */ > -static void *dax_insert_entry(struct xa_state *xas, > - struct address_space *mapping, struct vm_fault *vmf, > - void *entry, pfn_t pfn, unsigned long flags, bool dirty) > +static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf, > + void *entry, pfn_t pfn, unsigned long flags, > + unsigned int insert_flags) > { > + struct address_space *mapping = vmf->vma->vm_file->f_mapping; > void *new_entry = dax_make_entry(pfn, flags); > + bool dirty = insert_flags & DAX_IF_DIRTY; > + bool cow = insert_flags & DAX_IF_COW; > > if (dirty) > __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); I still think the __mark_inode_dirty should just be moved into the one caller that needs it.
> > > > if (dirty) > > __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); > > I still think the __mark_inode_dirty should just be moved into the one > caller that needs it. I found that the dirty flag will be used in the next few lines, so I keep this function inside. If I move it outside, the drity flag should be passed in as well. @@ -774,6 +780,9 @@ static void *dax_insert_entry(struct xa_state *xas, if (dirty) xas_set_mark(xas, PAGECACHE_TAG_DIRTY); + if (cow) + xas_set_mark(xas, PAGECACHE_TAG_TOWRITE); + xas_unlock_irq(xas); return entry; } So, may I ask what's your purpose for doing in that way? -- Thanks, Ruan Shiyang.
On Wed, Mar 03, 2021 at 09:41:54AM +0000, ruansy.fnst@fujitsu.com wrote: > > > > > > > if (dirty) > > > __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); > > > > I still think the __mark_inode_dirty should just be moved into the one > > caller that needs it. > > I found that the dirty flag will be used in the next few lines, so I keep > this function inside. If I move it outside, the drity flag should be passed > in as well. > > @@ -774,6 +780,9 @@ static void *dax_insert_entry(struct xa_state *xas, > if (dirty) > xas_set_mark(xas, PAGECACHE_TAG_DIRTY); > > + if (cow) > + xas_set_mark(xas, PAGECACHE_TAG_TOWRITE); > + > xas_unlock_irq(xas); > return entry; > } > > > So, may I ask what's your purpose for doing in that way? Oh, true. We can't just move that out as the xas needs to stay locked.
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/dax.c b/fs/dax.c index 748dfb89fb41..ec4b733e0b59 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -722,6 +722,9 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d return 0; } +#define DAX_IF_DIRTY (1 << 0) +#define DAX_IF_COW (1 << 1) + /* * By this point grab_mapping_entry() has ensured that we have a locked entry * of the appropriate size so we don't have to worry about downgrading PMDs to @@ -729,16 +732,19 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d * already in the tree, we will skip the insertion and just dirty the PMD as * appropriate. */ -static void *dax_insert_entry(struct xa_state *xas, - struct address_space *mapping, struct vm_fault *vmf, - void *entry, pfn_t pfn, unsigned long flags, bool dirty) +static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf, + void *entry, pfn_t pfn, unsigned long flags, + unsigned int insert_flags) { + struct address_space *mapping = vmf->vma->vm_file->f_mapping; void *new_entry = dax_make_entry(pfn, flags); + bool dirty = insert_flags & DAX_IF_DIRTY; + bool cow = insert_flags & DAX_IF_COW; if (dirty) __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); - if (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE)) { + if (cow || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) { unsigned long index = xas->xa_index; /* we are replacing a zero page with block mapping */ if (dax_is_pmd_entry(entry)) @@ -750,7 +756,7 @@ static void *dax_insert_entry(struct xa_state *xas, xas_reset(xas); xas_lock_irq(xas); - if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { + if (cow || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { void *old; dax_disassociate_entry(entry, mapping, false); @@ -774,6 +780,9 @@ static void *dax_insert_entry(struct xa_state *xas, if (dirty) xas_set_mark(xas, PAGECACHE_TAG_DIRTY); + if (cow) + xas_set_mark(xas, PAGECACHE_TAG_TOWRITE); + xas_unlock_irq(xas); return entry; } @@ -1100,8 +1109,7 @@ static vm_fault_t dax_load_hole(struct xa_state *xas, pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr)); vm_fault_t ret; - *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, - DAX_ZERO_PAGE, false); + *entry = dax_insert_entry(xas, vmf, *entry, pfn, DAX_ZERO_PAGE, 0); ret = vmf_insert_mixed(vmf->vma, vaddr, pfn); trace_dax_load_hole(inode, vmf, ret); @@ -1403,6 +1411,7 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, loff_t pos = (loff_t)xas->xa_offset << PAGE_SHIFT; bool write = vmf->flags & FAULT_FLAG_WRITE; bool sync = dax_fault_is_synchronous(flags, vmf->vma, iomap); + unsigned int insert_flags = 0; vm_fault_t ret = 0; int err = 0; pfn_t pfn; @@ -1426,8 +1435,14 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, if (err) goto error_fault; - entry = dax_insert_entry(xas, mapping, vmf, entry, pfn, 0, - write && !sync); + if (write) { + if (!sync) + insert_flags |= DAX_IF_DIRTY; + if (iomap->flags & IOMAP_F_SHARED) + insert_flags |= DAX_IF_COW; + } + + entry = dax_insert_entry(xas, vmf, entry, pfn, 0, insert_flags); if (write && srcmap->addr != iomap->addr) { err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr, false); @@ -1571,8 +1586,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, goto fallback; pfn = page_to_pfn_t(zero_page); - *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, - DAX_PMD | DAX_ZERO_PAGE, false); + *entry = dax_insert_entry(xas, vmf, *entry, pfn, + DAX_PMD | DAX_ZERO_PAGE, 0); if (arch_needs_pgtable_deposit()) { pgtable = pte_alloc_one(vma->vm_mm);