To copy source data to destance address before write. Change dax_iomap_pfn() to return the address as well in order to use it for performing a memcpy in case the type is IOMAP_COW.
dax_copy_edges() is a helper functions performs a copy from one part of the device to another for data not page aligned. Signed-off-by: Goldwyn Rodrigues <[email protected]> Signed-off-by: Shiyang Ruan <[email protected]> --- fs/dax.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 52 insertions(+), 4 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 88b93796855e..450baafe2ea4 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -984,7 +984,7 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos) } static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, - pfn_t *pfnp) + pfn_t *pfnp, void **addr) { const sector_t sector = dax_iomap_sector(iomap, pos); pgoff_t pgoff; @@ -996,11 +996,13 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, return rc; id = dax_read_lock(); length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size), - NULL, pfnp); + addr, pfnp); if (length < 0) { rc = length; goto out; } + if (!pfnp) + goto out_check_addr; rc = -EINVAL; if (PFN_PHYS(length) < size) goto out; @@ -1010,6 +1012,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, if (length > 1 && !pfn_t_devmap(*pfnp)) goto out; rc = 0; + +out_check_addr: + if (!addr) + goto out; + if (!*addr) + rc = -EFAULT; out: dax_read_unlock(id); return rc; @@ -1084,6 +1092,46 @@ int __dax_zero_page_range(struct block_device *bdev, } EXPORT_SYMBOL_GPL(__dax_zero_page_range); +/* + * dax_copy_edges - Copies the part of the pages not included in + * the write, but required for CoW because + * offset/offset+length are not page aligned. + */ +static int dax_copy_edges(struct inode *inode, loff_t pos, loff_t length, + struct iomap *srcmap, void *daddr) +{ + unsigned offset = pos & (PAGE_SIZE - 1); + loff_t end = pos + length; + loff_t pg_end = round_up(end, PAGE_SIZE); + void *saddr = 0; + int ret = 0; + + ret = dax_iomap_pfn(srcmap, pos, length, NULL, &saddr); + if (ret) + return ret; + /* + * Copy the first part of the page + * Note: we pass offset as length + */ + if (offset) { + if (saddr) + ret = memcpy_mcsafe(daddr, saddr, offset); + else + memset(daddr, 0, offset); + } + + /* Copy the last part of the range */ + if (end < pg_end) { + if (saddr) + ret = memcpy_mcsafe(daddr + offset + length, + saddr + offset + length, pg_end - end); + else + memset(daddr + offset + length, 0, + pg_end - end); + } + return ret; +} + static loff_t dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap, struct iomap *srcmap) @@ -1338,7 +1386,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, count_memcg_event_mm(vma->vm_mm, PGMAJFAULT); major = VM_FAULT_MAJOR; } - error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn); + error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn, NULL); if (error < 0) goto error_finish_iomap; @@ -1555,7 +1603,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, switch (iomap.type) { case IOMAP_MAPPED: - error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn); + error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn, NULL); if (error < 0) goto finish_iomap; -- 2.17.0
