> -----Original Message----- > From: Darrick J. Wong <djwong(a)kernel.org&gt; > Subject: Re: [PATCH v5 5/7] fsdax: Dedup file range to use a compare function > > On Tue, May 11, 2021 at 11:09:31AM +0800, Shiyang Ruan wrote: > > 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 */ > > Hmm, can you add an entry to the !IS_ENABLED(CONFIG_DAX) part of dax.h > that defines dax_dedupe_file_range_compare as a dummy function that returns > -EOPNOTSUPP? We try not to sprinkle preprocessor directives into the middle > of functions, per Linus rules. 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.

> > > + 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); > > I think this symbol belongs in fs/dax.c and the declaration in dax.h? 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.