[PATCH v2 4/5] erofs: use meta buffers for xattr operations

[Gao Xiang <hsiangkao@linux.alibaba.com>]

Get rid of old erofs_get_meta_page() within xattr operations by
using on-stack meta buffers in order to prepare subpage and folio
features.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/xattr.c | 134 ++++++++++++++---------------------------------
 1 file changed, 40 insertions(+), 94 deletions(-)

diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
index 01c581e93c5f..437ff6e7293d 100644
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -8,33 +8,13 @@
 
 struct xattr_iter {
 	struct super_block *sb;
-	struct page *page;
+	struct erofs_buf buf;
 	void *kaddr;
 
 	erofs_blk_t blkaddr;
 	unsigned int ofs;
 };
 
-static inline void xattr_iter_end(struct xattr_iter *it, bool atomic)
-{
-	/* the only user of kunmap() is 'init_inode_xattrs' */
-	if (!atomic)
-		kunmap(it->page);
-	else
-		kunmap_atomic(it->kaddr);
-
-	unlock_page(it->page);
-	put_page(it->page);
-}
-
-static inline void xattr_iter_end_final(struct xattr_iter *it)
-{
-	if (!it->page)
-		return;
-
-	xattr_iter_end(it, true);
-}
-
 static int init_inode_xattrs(struct inode *inode)
 {
 	struct erofs_inode *const vi = EROFS_I(inode);
@@ -43,7 +23,6 @@ static int init_inode_xattrs(struct inode *inode)
 	struct erofs_xattr_ibody_header *ih;
 	struct super_block *sb;
 	struct erofs_sb_info *sbi;
-	bool atomic_map;
 	int ret = 0;
 
 	/* the most case is that xattrs of this inode are initialized. */
@@ -91,26 +70,23 @@ static int init_inode_xattrs(struct inode *inode)
 
 	sb = inode->i_sb;
 	sbi = EROFS_SB(sb);
+	it.buf = __EROFS_BUF_INITIALIZER;
 	it.blkaddr = erofs_blknr(iloc(sbi, vi->nid) + vi->inode_isize);
 	it.ofs = erofs_blkoff(iloc(sbi, vi->nid) + vi->inode_isize);
 
-	it.page = erofs_get_meta_page(sb, it.blkaddr);
-	if (IS_ERR(it.page)) {
-		ret = PTR_ERR(it.page);
+	/* read in shared xattr array (non-atomic, see kmalloc below) */
+	it.kaddr = erofs_read_metabuf(&it.buf, sb, it.blkaddr, EROFS_KMAP);
+	if (IS_ERR(it.kaddr)) {
+		ret = PTR_ERR(it.kaddr);
 		goto out_unlock;
 	}
 
-	/* read in shared xattr array (non-atomic, see kmalloc below) */
-	it.kaddr = kmap(it.page);
-	atomic_map = false;
-
 	ih = (struct erofs_xattr_ibody_header *)(it.kaddr + it.ofs);
-
 	vi->xattr_shared_count = ih->h_shared_count;
 	vi->xattr_shared_xattrs = kmalloc_array(vi->xattr_shared_count,
 						sizeof(uint), GFP_KERNEL);
 	if (!vi->xattr_shared_xattrs) {
-		xattr_iter_end(&it, atomic_map);
+		erofs_put_metabuf(&it.buf);
 		ret = -ENOMEM;
 		goto out_unlock;
 	}
@@ -122,25 +98,22 @@ static int init_inode_xattrs(struct inode *inode)
 		if (it.ofs >= EROFS_BLKSIZ) {
 			/* cannot be unaligned */
 			DBG_BUGON(it.ofs != EROFS_BLKSIZ);
-			xattr_iter_end(&it, atomic_map);
 
-			it.page = erofs_get_meta_page(sb, ++it.blkaddr);
-			if (IS_ERR(it.page)) {
+			it.kaddr = erofs_read_metabuf(&it.buf, sb, ++it.blkaddr,
+						      EROFS_KMAP);
+			if (IS_ERR(it.kaddr)) {
 				kfree(vi->xattr_shared_xattrs);
 				vi->xattr_shared_xattrs = NULL;
-				ret = PTR_ERR(it.page);
+				ret = PTR_ERR(it.kaddr);
 				goto out_unlock;
 			}
-
-			it.kaddr = kmap_atomic(it.page);
-			atomic_map = true;
 			it.ofs = 0;
 		}
 		vi->xattr_shared_xattrs[i] =
 			le32_to_cpu(*(__le32 *)(it.kaddr + it.ofs));
 		it.ofs += sizeof(__le32);
 	}
-	xattr_iter_end(&it, atomic_map);
+	erofs_put_metabuf(&it.buf);
 
 	/* paired with smp_mb() at the beginning of the function. */
 	smp_mb();
@@ -172,19 +145,11 @@ static inline int xattr_iter_fixup(struct xattr_iter *it)
 	if (it->ofs < EROFS_BLKSIZ)
 		return 0;
 
-	xattr_iter_end(it, true);
-
 	it->blkaddr += erofs_blknr(it->ofs);
-
-	it->page = erofs_get_meta_page(it->sb, it->blkaddr);
-	if (IS_ERR(it->page)) {
-		int err = PTR_ERR(it->page);
-
-		it->page = NULL;
-		return err;
-	}
-
-	it->kaddr = kmap_atomic(it->page);
+	it->kaddr = erofs_read_metabuf(&it->buf, it->sb, it->blkaddr,
+				       EROFS_KMAP_ATOMIC);
+	if (IS_ERR(it->kaddr))
+		return PTR_ERR(it->kaddr);
 	it->ofs = erofs_blkoff(it->ofs);
 	return 0;
 }
@@ -207,11 +172,10 @@ static int inline_xattr_iter_begin(struct xattr_iter *it,
 	it->blkaddr = erofs_blknr(iloc(sbi, vi->nid) + inline_xattr_ofs);
 	it->ofs = erofs_blkoff(iloc(sbi, vi->nid) + inline_xattr_ofs);
 
-	it->page = erofs_get_meta_page(inode->i_sb, it->blkaddr);
-	if (IS_ERR(it->page))
-		return PTR_ERR(it->page);
-
-	it->kaddr = kmap_atomic(it->page);
+	it->kaddr = erofs_read_metabuf(&it->buf, inode->i_sb, it->blkaddr,
+				       EROFS_KMAP_ATOMIC);
+	if (IS_ERR(it->kaddr))
+		return PTR_ERR(it->kaddr);
 	return vi->xattr_isize - xattr_header_sz;
 }
 
@@ -272,7 +236,7 @@ static int xattr_foreach(struct xattr_iter *it,
 			it->ofs = 0;
 		}
 
-		slice = min_t(unsigned int, PAGE_SIZE - it->ofs,
+		slice = min_t(unsigned int, EROFS_BLKSIZ - it->ofs,
 			      entry.e_name_len - processed);
 
 		/* handle name */
@@ -307,7 +271,7 @@ static int xattr_foreach(struct xattr_iter *it,
 			it->ofs = 0;
 		}
 
-		slice = min_t(unsigned int, PAGE_SIZE - it->ofs,
+		slice = min_t(unsigned int, EROFS_BLKSIZ - it->ofs,
 			      value_sz - processed);
 		op->value(it, processed, it->kaddr + it->ofs, slice);
 		it->ofs += slice;
@@ -386,8 +350,6 @@ static int inline_getxattr(struct inode *inode, struct getxattr_iter *it)
 		if (ret != -ENOATTR)
 			break;
 	}
-	xattr_iter_end_final(&it->it);
-
 	return ret ? ret : it->buffer_size;
 }
 
@@ -404,26 +366,16 @@ static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
 			xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);
 
 		it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);
-
-		if (!i || blkaddr != it->it.blkaddr) {
-			if (i)
-				xattr_iter_end(&it->it, true);
-
-			it->it.page = erofs_get_meta_page(sb, blkaddr);
-			if (IS_ERR(it->it.page))
-				return PTR_ERR(it->it.page);
-
-			it->it.kaddr = kmap_atomic(it->it.page);
-			it->it.blkaddr = blkaddr;
-		}
+		it->it.kaddr = erofs_read_metabuf(&it->it.buf, sb, blkaddr,
+						  EROFS_KMAP_ATOMIC);
+		if (IS_ERR(it->it.kaddr))
+			return PTR_ERR(it->it.kaddr);
+		it->it.blkaddr = blkaddr;
 
 		ret = xattr_foreach(&it->it, &find_xattr_handlers, NULL);
 		if (ret != -ENOATTR)
 			break;
 	}
-	if (vi->xattr_shared_count)
-		xattr_iter_end_final(&it->it);
-
 	return ret ? ret : it->buffer_size;
 }
 
@@ -452,10 +404,11 @@ int erofs_getxattr(struct inode *inode, int index,
 		return ret;
 
 	it.index = index;
-
 	it.name.len = strlen(name);
 	if (it.name.len > EROFS_NAME_LEN)
 		return -ERANGE;
+
+	it.it.buf = __EROFS_BUF_INITIALIZER;
 	it.name.name = name;
 
 	it.buffer = buffer;
@@ -465,6 +418,7 @@ int erofs_getxattr(struct inode *inode, int index,
 	ret = inline_getxattr(inode, &it);
 	if (ret == -ENOATTR)
 		ret = shared_getxattr(inode, &it);
+	erofs_put_metabuf(&it.it.buf);
 	return ret;
 }
 
@@ -607,7 +561,6 @@ static int inline_listxattr(struct listxattr_iter *it)
 		if (ret)
 			break;
 	}
-	xattr_iter_end_final(&it->it);
 	return ret ? ret : it->buffer_ofs;
 }
 
@@ -625,25 +578,16 @@ static int shared_listxattr(struct listxattr_iter *it)
 			xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);
 
 		it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);
-		if (!i || blkaddr != it->it.blkaddr) {
-			if (i)
-				xattr_iter_end(&it->it, true);
-
-			it->it.page = erofs_get_meta_page(sb, blkaddr);
-			if (IS_ERR(it->it.page))
-				return PTR_ERR(it->it.page);
-
-			it->it.kaddr = kmap_atomic(it->it.page);
-			it->it.blkaddr = blkaddr;
-		}
+		it->it.kaddr = erofs_read_metabuf(&it->it.buf, sb, blkaddr,
+						  EROFS_KMAP_ATOMIC);
+		if (IS_ERR(it->it.kaddr))
+			return PTR_ERR(it->it.kaddr);
+		it->it.blkaddr = blkaddr;
 
 		ret = xattr_foreach(&it->it, &list_xattr_handlers, NULL);
 		if (ret)
 			break;
 	}
-	if (vi->xattr_shared_count)
-		xattr_iter_end_final(&it->it);
-
 	return ret ? ret : it->buffer_ofs;
 }
 
@@ -659,6 +603,7 @@ ssize_t erofs_listxattr(struct dentry *dentry,
 	if (ret)
 		return ret;
 
+	it.it.buf = __EROFS_BUF_INITIALIZER;
 	it.dentry = dentry;
 	it.buffer = buffer;
 	it.buffer_size = buffer_size;
@@ -667,9 +612,10 @@ ssize_t erofs_listxattr(struct dentry *dentry,
 	it.it.sb = dentry->d_sb;
 
 	ret = inline_listxattr(&it);
-	if (ret < 0 && ret != -ENOATTR)
-		return ret;
-	return shared_listxattr(&it);
+	if (ret >= 0 || ret == -ENOATTR)
+		ret = shared_listxattr(&it);
+	erofs_put_metabuf(&it.it.buf);
+	return ret;
 }
 
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
-- 
2.24.4