Messages in this thread |  | | Subject | Re: [PATCH 4/7] fsdax: Replace mmap entry in case of CoW | From | Ruan Shiyang <> | Date | Wed, 17 Feb 2021 11:06:55 +0800 |
| |
On 2021/2/16 下午9:11, David Sterba wrote: > On Mon, Feb 08, 2021 at 01:09:21AM +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@cn.fujitsu.com> >> --- >> fs/dax.c | 31 +++++++++++++++++++++++-------- >> 1 file changed, 23 insertions(+), 8 deletions(-) >> >> diff --git a/fs/dax.c b/fs/dax.c >> index b2195cbdf2dc..29698a3d2e37 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 (1ULL << 0) >> +#define DAX_IF_COW (1ULL << 1) > > The constants are ULL, but I see other flags only 'unsigned long' > >> + >> /* >> * 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 >> @@ -731,14 +734,16 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d >> */ >> 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) >> + void *entry, pfn_t pfn, unsigned long flags, bool insert_flags) > > insert_flags is bool > >> { >> void *new_entry = dax_make_entry(pfn, flags); >> + bool dirty = insert_flags & DAX_IF_DIRTY; > > "insert_flags & DAX_IF_DIRTY" is "bool & ULL", this can't be right
This is a mistake caused by rebasing my old version patchset. Thanks for pointing out. I'll fix this in next version. > >> + bool cow = insert_flags & DAX_IF_COW; > > Same > >> >> 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 +755,7 @@ 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 +779,9 @@ 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; >> } >> @@ -1319,6 +1327,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, >> void *entry; >> pfn_t pfn; >> void *kaddr; >> + unsigned long insert_flags = 0; >> >> trace_dax_pte_fault(inode, vmf, ret); >> /* >> @@ -1444,8 +1453,10 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, >> >> goto finish_iomap; >> case IOMAP_UNWRITTEN: >> - if (write && iomap.flags & IOMAP_F_SHARED) >> + if (write && (iomap.flags & IOMAP_F_SHARED)) { >> + insert_flags |= DAX_IF_COW; > > Here's an example of 'unsigned long = unsigned long long', though it'll > work, it would be better to unify all the types.
Yes, I'll fix it.
-- Thanks, Ruan Shiyang. > >> goto cow; >> + } >> fallthrough; >> case IOMAP_HOLE: >> if (!write) { >> @@ -1555,6 +1566,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, >> int error; >> pfn_t pfn; >> void *kaddr; >> + unsigned long insert_flags = 0; >> >> /* >> * Check whether offset isn't beyond end of file now. Caller is >> @@ -1670,14 +1682,17 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, >> result = vmf_insert_pfn_pmd(vmf, pfn, write); >> break; >> case IOMAP_UNWRITTEN: >> - if (write && iomap.flags & IOMAP_F_SHARED) >> + if (write && (iomap.flags & IOMAP_F_SHARED)) { >> + insert_flags |= DAX_IF_COW; >> goto cow; >> + } >> fallthrough; >> case IOMAP_HOLE: >> - if (WARN_ON_ONCE(write)) >> + if (!write) { >> + result = dax_pmd_load_hole(&xas, vmf, &iomap, &entry); >> break; >> - result = dax_pmd_load_hole(&xas, vmf, &iomap, &entry); >> - break; >> + } >> + fallthrough; >> default: >> WARN_ON_ONCE(1); >> break; >> -- >> 2.30.0 >> >> > >
|  |