In the case where the iomap is a write operation and iomap is not equal to srcmap after iomap_begin, we consider it is a CoW operation. The destance extent which iomap indicated is new allocated extent. So, it is needed to copy the data from srcmap to new allocated extent. In theory, it is better to copy the head and tail ranges which is outside of the non-aligned area instead of copying the whole aligned range. But in dax page fault, it will always be an aligned range. So, we have to copy the whole range in this case. Signed-off-by: Shiyang Ruan <ruansy.fnst(a)fujitsu.com&gt; Reviewed-by: Christoph Hellwig <hch(a)lst.de&gt; --- fs/dax.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 81 insertions(+), 5 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index bf3fc8242e6c..f0249bb1d46a 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1038,6 +1038,61 @@ static int dax_iomap_direct_access(struct iomap *iomap, loff_t pos, size_t size, return rc; } +/** + * dax_iomap_cow_copy(): Copy the data from source to destination before write. + * @pos: address to do copy from. + * @length: size of copy operation. + * @align_size: aligned w.r.t align_size (either PMD_SIZE or PAGE_SIZE) + * @srcmap: iomap srcmap + * @daddr: destination address to copy to. + * + * This can be called from two places. Either during DAX write fault, to copy + * the length size data to daddr. Or, while doing normal DAX write operation, + * dax_iomap_actor() might call this to do the copy of either start or end + * unaligned address. In this case the rest of the copy of aligned ranges is + * taken care by dax_iomap_actor() itself. + * Also, note DAX fault will always result in aligned pos and pos + length. + */ +static int dax_iomap_cow_copy(loff_t pos, loff_t length, size_t align_size, + struct iomap *srcmap, void *daddr) +{ + loff_t head_off = pos & (align_size - 1); + size_t size = ALIGN(head_off + length, align_size); + loff_t end = pos + length; + loff_t pg_end = round_up(end, align_size); + bool copy_all = head_off == 0 && end == pg_end; + void *saddr = 0; + int ret = 0; + + ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL); + if (ret) + return ret; + + if (copy_all) { + ret = copy_mc_to_kernel(daddr, saddr, length); + return ret ? -EIO : 0; + } + + /* Copy the head part of the range. Note: we pass offset as length. */ + if (head_off) { + ret = copy_mc_to_kernel(daddr, saddr, head_off); + if (ret) + return -EIO; + } + + /* Copy the tail part of the range */ + if (end < pg_end) { + loff_t tail_off = head_off + length; + loff_t tail_len = pg_end - end; + + ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off, + tail_len); + if (ret) + return -EIO; + } + return 0; +} + /* * The user has performed a load from a hole in the file. Allocating a new * page in the file would cause excessive storage usage for workloads with @@ -1167,11 +1222,12 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct dax_device *dax_dev = iomap->dax_dev; struct iov_iter *iter = data; loff_t end = pos + length, done = 0; + bool write = iov_iter_rw(iter) == WRITE; ssize_t ret = 0; size_t xfer; int id; - if (iov_iter_rw(iter) == READ) { + if (!write) { end = min(end, i_size_read(inode)); if (pos >= end) return 0; @@ -1180,7 +1236,12 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, return iov_iter_zero(min(length, end - pos), iter); } - if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED)) + /* + * In DAX mode, we allow either pure overwrites of written extents, or + * writes to unwritten extents as part of a copy-on-write operation. + */ + if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED && + !(iomap->flags & IOMAP_F_SHARED))) return -EIO; /* @@ -1219,6 +1280,13 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, break; } + if (write && srcmap->addr != iomap->addr) { + ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap, + kaddr); + if (ret) + break; + } + map_len = PFN_PHYS(map_len); kaddr += offset; map_len -= offset; @@ -1230,7 +1298,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, * validated via access_ok() in either vfs_read() or * vfs_write(), depending on which operation we are doing. */ - if (iov_iter_rw(iter) == WRITE) + if (write) xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); else @@ -1382,6 +1450,7 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, unsigned long entry_flags = pmd ? DAX_PMD : 0; int err = 0; pfn_t pfn; + void *kaddr; /* if we are reading UNWRITTEN and HOLE, return a hole. */ if (!write && @@ -1392,18 +1461,25 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, return dax_pmd_load_hole(xas, vmf, iomap, entry); } - if (iomap->type != IOMAP_MAPPED) { + if (iomap->type != IOMAP_MAPPED && !(iomap->flags & IOMAP_F_SHARED)) { WARN_ON_ONCE(1); return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS; } - err = dax_iomap_direct_access(iomap, pos, size, NULL, &pfn); + err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn); if (err) return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err); *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, entry_flags, write && !sync); + if (write && + srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) { + err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr); + if (err) + return dax_fault_return(err); + } + if (sync) return dax_fault_synchronous_pfnp(pfnp, pfn); -- 2.31.1

Punch hole on a reflinked file needs dax_copy_edge() too. Otherwise, data in not aligned area will be not correct. So, add the srcmap to dax_iomap_zero() and replace memset() as dax_copy_edge(). Signed-off-by: Shiyang Ruan <ruansy.fnst(a)fujitsu.com&gt; Reviewed-by: Ritesh Harjani <riteshh(a)linux.ibm.com&gt; --- fs/dax.c | 25 +++++++++++++++---------- fs/iomap/buffered-io.c | 2 +- include/linux/dax.h | 3 ++- 3 files changed, 18 insertions(+), 12 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index ef0e564e7904..ee9d28a79bfb 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1186,7 +1186,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, } #endif /* CONFIG_FS_DAX_PMD */ -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap) +s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, + struct iomap *srcmap) { sector_t sector = iomap_sector(iomap, pos & PAGE_MASK); pgoff_t pgoff; @@ -1208,19 +1209,23 @@ s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap) if (page_aligned) rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1); - else + else { rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL); - if (rc < 0) { - dax_read_unlock(id); - return rc; - } - - if (!page_aligned) { - memset(kaddr + offset, 0, size); + if (rc < 0) + goto out; + if (iomap->addr != srcmap->addr) { + rc = dax_iomap_cow_copy(offset, size, PAGE_SIZE, srcmap, + kaddr); + if (rc < 0) + goto out; + } else + memset(kaddr + offset, 0, size); dax_flush(iomap->dax_dev, kaddr + offset, size); } + +out: dax_read_unlock(id); - return size; + return rc < 0 ? rc : size; } static loff_t diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index f2cd2034a87b..2734955ea67f 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -933,7 +933,7 @@ static loff_t iomap_zero_range_actor(struct inode *inode, loff_t pos, s64 bytes; if (IS_DAX(inode)) - bytes = dax_iomap_zero(pos, length, iomap); + bytes = dax_iomap_zero(pos, length, iomap, srcmap); else bytes = iomap_zero(inode, pos, length, iomap, srcmap); if (bytes < 0) diff --git a/include/linux/dax.h b/include/linux/dax.h index b52f084aa643..3275e01ed33d 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -237,7 +237,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index); int dax_invalidate_mapping_entry_sync(struct address_space *mapping, pgoff_t index); -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap); +s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, + struct iomap *srcmap); static inline bool dax_mapping(struct address_space *mapping) { return mapping->host && IS_DAX(mapping->host); -- 2.31.1

With dax we cannot deal with readpage() etc. So, we create a dax comparison funciton which is similar with vfs_dedupe_file_range_compare(). And introduce dax_remap_file_range_prep() for filesystem use. Signed-off-by: Goldwyn Rodrigues <rgoldwyn(a)suse.com&gt; Signed-off-by: Shiyang Ruan <ruansy.fnst(a)fujitsu.com&gt; --- fs/dax.c | 56 +++++++++++++++++++++++++++++++++++++++++++ fs/remap_range.c | 57 +++++++++++++++++++++++++++++++++++++------- fs/xfs/xfs_reflink.c | 8 +++++-- include/linux/dax.h | 4 ++++ include/linux/fs.h | 12 ++++++---- 5 files changed, 123 insertions(+), 14 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index ee9d28a79bfb..dedf1be0155c 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1853,3 +1853,59 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, return dax_insert_pfn_mkwrite(vmf, pfn, order); } EXPORT_SYMBOL_GPL(dax_finish_sync_fault); + +static loff_t dax_range_compare_actor(struct inode *ino1, loff_t pos1, + struct inode *ino2, loff_t pos2, loff_t len, void *data, + struct iomap *smap, struct iomap *dmap) +{ + void *saddr, *daddr; + bool *same = data; + int ret; + + if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE) { + *same = true; + return len; + } + + if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) { + *same = false; + return 0; + } + + ret = dax_iomap_direct_access(smap, pos1, ALIGN(pos1 + len, PAGE_SIZE), + &saddr, NULL); + if (ret < 0) + return -EIO; + + ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE), + &daddr, NULL); + if (ret < 0) + return -EIO; + + *same = !memcmp(saddr, daddr, len); + return len; +} + +int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff, + struct inode *dest, loff_t destoff, loff_t len, bool *is_same, + const struct iomap_ops *ops) +{ + int id, ret = 0; + + id = dax_read_lock(); + while (len) { + ret = iomap_apply2(src, srcoff, dest, destoff, len, 0, ops, + is_same, dax_range_compare_actor); + if (ret < 0 || !*is_same) + goto out; + + len -= ret; + srcoff += ret; + destoff += ret; + } + ret = 0; +out: + dax_read_unlock(id); + return ret; +} +EXPORT_SYMBOL_GPL(dax_dedupe_file_range_compare); diff --git a/fs/remap_range.c b/fs/remap_range.c index e4a5fdd7ad7b..7bc4c8e3aa9f 100644 --- a/fs/remap_range.c +++ b/fs/remap_range.c @@ -14,6 +14,7 @@ #include <linux/compat.h> #include <linux/mount.h> #include <linux/fs.h> +#include <linux/dax.h> #include "internal.h" #include <linux/uaccess.h> @@ -199,9 +200,9 @@ static void vfs_unlock_two_pages(struct page *page1, struct page *page2) * Compare extents of two files to see if they are the same. * Caller must have locked both inodes to prevent write races. */ -static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, - struct inode *dest, loff_t destoff, - loff_t len, bool *is_same) +int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, + struct inode *dest, loff_t destoff, + loff_t len, bool *is_same) { loff_t src_poff; loff_t dest_poff; @@ -280,6 +281,7 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, out_error: return error; } +EXPORT_SYMBOL(vfs_dedupe_file_range_compare); /* * Check that the two inodes are eligible for cloning, the ranges make @@ -289,9 +291,11 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, * If there's an error, then the usual negative error code is returned. * Otherwise returns 0 with *len set to the request length. */ -int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, - struct file *file_out, loff_t pos_out, - loff_t *len, unsigned int remap_flags) +static int +__generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *len, unsigned int remap_flags, + const struct iomap_ops *dax_read_ops) { struct inode *inode_in = file_inode(file_in); struct inode *inode_out = file_inode(file_out); @@ -351,8 +355,17 @@ int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, if (remap_flags & REMAP_FILE_DEDUP) { bool is_same = false; - ret = vfs_dedupe_file_range_compare(inode_in, pos_in, - inode_out, pos_out, *len, &is_same); + if (!IS_DAX(inode_in)) + ret = vfs_dedupe_file_range_compare(inode_in, pos_in, + inode_out, pos_out, *len, &is_same); +#ifdef CONFIG_FS_DAX + else if (dax_read_ops) + ret = dax_dedupe_file_range_compare(inode_in, pos_in, + inode_out, pos_out, *len, &is_same, + dax_read_ops); +#endif /* CONFIG_FS_DAX */ + else + return -EINVAL; if (ret) return ret; if (!is_same) @@ -370,6 +383,34 @@ int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, return ret; } + +#ifdef CONFIG_FS_DAX +int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *len, unsigned int remap_flags, + const struct iomap_ops *ops) +{ + return __generic_remap_file_range_prep(file_in, pos_in, file_out, + pos_out, len, remap_flags, ops); +} +#else +int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *len, unsigned int remap_flags, + const struct iomap_ops *ops) +{ + return -EOPNOTSUPP; +} +#endif /* CONFIG_FS_DAX */ +EXPORT_SYMBOL(dax_remap_file_range_prep); + +int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *len, unsigned int remap_flags) +{ + return __generic_remap_file_range_prep(file_in, pos_in, file_out, + pos_out, len, remap_flags, NULL); +} EXPORT_SYMBOL(generic_remap_file_range_prep); loff_t do_clone_file_range(struct file *file_in, loff_t pos_in, diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index 060695d6d56a..d25434f93235 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -1329,8 +1329,12 @@ xfs_reflink_remap_prep( if (IS_DAX(inode_in) || IS_DAX(inode_out)) goto out_unlock; - ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out, - len, remap_flags); + if (!IS_DAX(inode_in)) + ret = generic_remap_file_range_prep(file_in, pos_in, file_out, + pos_out, len, remap_flags); + else + ret = dax_remap_file_range_prep(file_in, pos_in, file_out, + pos_out, len, remap_flags, &xfs_read_iomap_ops); if (ret || *len == 0) goto out_unlock; diff --git a/include/linux/dax.h b/include/linux/dax.h index 3275e01ed33d..32e1c34349f2 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -239,6 +239,10 @@ int dax_invalidate_mapping_entry_sync(struct address_space *mapping, pgoff_t index); s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, struct iomap *srcmap); +int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff, + struct inode *dest, loff_t destoff, + loff_t len, bool *is_same, + const struct iomap_ops *ops); static inline bool dax_mapping(struct address_space *mapping) { return mapping->host && IS_DAX(mapping->host); diff --git a/include/linux/fs.h b/include/linux/fs.h index c3c88fdb9b2a..e2c348553d87 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -71,6 +71,7 @@ struct fsverity_operations; struct fs_context; struct fs_parameter_spec; struct fileattr; +struct iomap_ops; extern void __init inode_init(void); extern void __init inode_init_early(void); @@ -2126,10 +2127,13 @@ extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *, extern ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in, struct file *file_out, loff_t pos_out, size_t len, unsigned int flags); -extern int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, - struct file *file_out, loff_t pos_out, - loff_t *count, - unsigned int remap_flags); +int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *count, unsigned int remap_flags); +int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in, + struct file *file_out, loff_t pos_out, + loff_t *len, unsigned int remap_flags, + const struct iomap_ops *ops); extern loff_t do_clone_file_range(struct file *file_in, loff_t pos_in, struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags); -- 2.31.1

Introduce xfs_mmaplock_two_inodes_and_break_dax_layout() for dax files who are going to be deduped. After that, call compare range function only when files are both DAX or not. Signed-off-by: Shiyang Ruan <ruansy.fnst(a)fujitsu.com&gt; --- fs/xfs/xfs_file.c | 2 +- fs/xfs/xfs_inode.c | 66 +++++++++++++++++++++++++++++++++++++++++++- fs/xfs/xfs_inode.h | 1 + fs/xfs/xfs_reflink.c | 4 +-- 4 files changed, 69 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 38d8eca05aee..bd5002d38df4 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -823,7 +823,7 @@ xfs_wait_dax_page( xfs_ilock(ip, XFS_MMAPLOCK_EXCL); } -static int +int xfs_break_dax_layouts( struct inode *inode, bool *retry) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 0369eb22c1bb..0774b6e2b940 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -3711,6 +3711,64 @@ xfs_iolock_two_inodes_and_break_layout( return 0; } +static int +xfs_mmaplock_two_inodes_and_break_dax_layout( + struct inode *src, + struct inode *dest) +{ + int error, attempts = 0; + bool retry; + struct xfs_inode *ip0, *ip1; + struct page *page; + struct xfs_log_item *lp; + + if (src > dest) + swap(src, dest); + ip0 = XFS_I(src); + ip1 = XFS_I(dest); + +again: + retry = false; + /* Lock the first inode */ + xfs_ilock(ip0, XFS_MMAPLOCK_EXCL); + error = xfs_break_dax_layouts(src, &retry); + if (error || retry) { + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL); + goto again; + } + + if (src == dest) + return 0; + + /* Nested lock the second inode */ + lp = &ip0->i_itemp->ili_item; + if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags)) { + if (!xfs_ilock_nowait(ip1, + xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1))) { + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL); + if ((++attempts % 5) == 0) + delay(1); /* Don't just spin the CPU */ + goto again; + } + } else + xfs_ilock(ip1, xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1)); + /* + * We cannot use xfs_break_dax_layouts() directly here because it may + * need to unlock & lock the XFS_MMAPLOCK_EXCL which is not suitable + * for this nested lock case. + */ + page = dax_layout_busy_page(dest->i_mapping); + if (page) { + if (page_ref_count(page) != 1) { + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL); + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL); + goto again; + } + } + + return 0; +} + /* * Lock two inodes so that userspace cannot initiate I/O via file syscalls or * mmap activity. @@ -3721,10 +3779,16 @@ xfs_ilock2_io_mmap( struct xfs_inode *ip2) { int ret; + struct inode *ino1 = VFS_I(ip1); + struct inode *ino2 = VFS_I(ip2); - ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2)); + ret = xfs_iolock_two_inodes_and_break_layout(ino1, ino2); if (ret) return ret; + + if (IS_DAX(ino1) && IS_DAX(ino2)) + return xfs_mmaplock_two_inodes_and_break_dax_layout(ino1, ino2); + if (ip1 == ip2) xfs_ilock(ip1, XFS_MMAPLOCK_EXCL); else diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index ca826cfba91c..2d0b344fb100 100644 --- a/fs/xfs/xfs_inode.h +++ b/fs/xfs/xfs_inode.h @@ -457,6 +457,7 @@ enum xfs_prealloc_flags { int xfs_update_prealloc_flags(struct xfs_inode *ip, enum xfs_prealloc_flags flags); +int xfs_break_dax_layouts(struct inode *inode, bool *retry); int xfs_break_layouts(struct inode *inode, uint *iolock, enum layout_break_reason reason); diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index 9a780948dbd0..ff308304c5cd 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -1324,8 +1324,8 @@ xfs_reflink_remap_prep( if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest)) goto out_unlock; - /* Don't share DAX file data for now. */ - if (IS_DAX(inode_in) || IS_DAX(inode_out)) + /* Don't share DAX file data with non-DAX file. */ + if (IS_DAX(inode_in) != IS_DAX(inode_out)) goto out_unlock; if (!IS_DAX(inode_in)) -- 2.31.1

On Tue, May 11, 2021 at 11:09:27AM +0800, Shiyang Ruan wrote: Nit: Linus has asked us not to continue the use of loff_t for file io length. Could you change this to 'uint64_t length', please? (Assuming we even need the extra length bits?) With that fixed up... Reviewed-by: Darrick J. Wong <djwong(a)kernel.org&gt; --D Other nit: head_off = round_down(pos, align_size); ? > + size_t size = ALIGN(head_off + length, align_size); > + loff_t end = pos + length; > + loff_t pg_end = round_up(end, align_size); > + bool copy_all = head_off == 0 && end == pg_end; > + void *saddr = 0; > + int ret = 0; > + > + ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL); > + if (ret) > + return ret; > + > + if (copy_all) { > + ret = copy_mc_to_kernel(daddr, saddr, length); > + return ret ? -EIO : 0; > + } > + > + /* Copy the head part of the range. Note: we pass offset as length. */ > + if (head_off) { > + ret = copy_mc_to_kernel(daddr, saddr, head_off); > + if (ret) > + return -EIO; > + } > + > + /* Copy the tail part of the range */ > + if (end < pg_end) { > + loff_t tail_off = head_off + length; > + loff_t tail_len = pg_end - end; > + > + ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off, > + tail_len); > + if (ret) > + return -EIO; > + } > + return 0; > +} > + > /* > * The user has performed a load from a hole in the file. Allocating a new > * page in the file would cause excessive storage usage for workloads with > @@ -1167,11 +1222,12 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > struct dax_device *dax_dev = iomap->dax_dev; > struct iov_iter *iter = data; > loff_t end = pos + length, done = 0; > + bool write = iov_iter_rw(iter) == WRITE; > ssize_t ret = 0; > size_t xfer; > int id; > > - if (iov_iter_rw(iter) == READ) { > + if (!write) { > end = min(end, i_size_read(inode)); > if (pos >= end) > return 0; > @@ -1180,7 +1236,12 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > return iov_iter_zero(min(length, end - pos), iter); > } > > - if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED)) > + /* > + * In DAX mode, we allow either pure overwrites of written extents, or > + * writes to unwritten extents as part of a copy-on-write operation. > + */ > + if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED && > + !(iomap->flags & IOMAP_F_SHARED))) > return -EIO; > > /* > @@ -1219,6 +1280,13 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > break; > } > > + if (write && srcmap->addr != iomap->addr) { > + ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap, > + kaddr); > + if (ret) > + break; > + } > + > map_len = PFN_PHYS(map_len); > kaddr += offset; > map_len -= offset; > @@ -1230,7 +1298,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > * validated via access_ok() in either vfs_read() or > * vfs_write(), depending on which operation we are doing. > */ > - if (iov_iter_rw(iter) == WRITE) > + if (write) > xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr, > map_len, iter); > else > @@ -1382,6 +1450,7 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, > unsigned long entry_flags = pmd ? DAX_PMD : 0; > int err = 0; > pfn_t pfn; > + void *kaddr; > > /* if we are reading UNWRITTEN and HOLE, return a hole. */ > if (!write && > @@ -1392,18 +1461,25 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp, > return dax_pmd_load_hole(xas, vmf, iomap, entry); > } > > - if (iomap->type != IOMAP_MAPPED) { > + if (iomap->type != IOMAP_MAPPED && !(iomap->flags & IOMAP_F_SHARED)) { > WARN_ON_ONCE(1); > return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS; > } > > - err = dax_iomap_direct_access(iomap, pos, size, NULL, &pfn); > + err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn); > if (err) > return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err); > > *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, entry_flags, > write && !sync); > > + if (write && > + srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) { > + err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr); > + if (err) > + return dax_fault_return(err); > + } > + > if (sync) > return dax_fault_synchronous_pfnp(pfnp, pfn); > > -- > 2.31.1 > > >

On Tue, May 11, 2021 at 11:09:29AM +0800, Shiyang Ruan wrote: Why isn't this "if (srcmap->type != IOMAP_HOLE)" ? I suppose it has the same effect, since @iomap should never be a hole and we should never have a @srcmap that's the same as @iomap, but still, we use IOMAP_HOLE checks in most other parts of fs/iomap/. Other than that, the logic looks decent to me. --D > + rc = dax_iomap_cow_copy(offset, size, PAGE_SIZE, srcmap, > + kaddr); > + if (rc < 0) > + goto out; > + } else > + memset(kaddr + offset, 0, size); > dax_flush(iomap->dax_dev, kaddr + offset, size); > } > + > +out: > dax_read_unlock(id); > - return size; > + return rc < 0 ? rc : size; > } > > static loff_t > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index f2cd2034a87b..2734955ea67f 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -933,7 +933,7 @@ static loff_t iomap_zero_range_actor(struct inode *inode, loff_t pos, > s64 bytes; > > if (IS_DAX(inode)) > - bytes = dax_iomap_zero(pos, length, iomap); > + bytes = dax_iomap_zero(pos, length, iomap, srcmap); > else > bytes = iomap_zero(inode, pos, length, iomap, srcmap); > if (bytes < 0) > diff --git a/include/linux/dax.h b/include/linux/dax.h > index b52f084aa643..3275e01ed33d 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -237,7 +237,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, > int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index); > int dax_invalidate_mapping_entry_sync(struct address_space *mapping, > pgoff_t index); > -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap); > +s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, > + struct iomap *srcmap); > static inline bool dax_mapping(struct address_space *mapping) > { > return mapping->host && IS_DAX(mapping->host); > -- > 2.31.1 > > >

Yes, I misunderstood here. OK. -- Thanks, Ruan Shiyang.

According to its caller `iomap_zero_range_actor()`, whether srcmap->type is IOMAP_HOLE has already been checked before `dax_iomap_zero()`. So the check you suggested will always be true... -- Thanks, Ruan Shiyang.

You are right. Should pass pos here. Thanks for pointing out. -- Thanks, Ruan Shiyang.

I found that it's ok to build without the #ifdef and #endif here, even though CONFIG_FS_DAX is disabled. And like other dax functions in fs/dax.c, such as dax_iomap_rw(), it is declared in include/linux/dax.h without IS_ENABLED() or #ifdef wrapped. And xfs calls it directly and it won't cause build error. So, I think I could just remove the #ifdef here, but I am not sure if this obeys the rule. For the function name, it does should belong to fs/dax. But if so, __generic_remap_file_range_prep() needs to be called in fs/dax. I don't think this is good. -- Thanks, Ruan Shiyang.