[08/22] ext4: kill off struct dx_root
diff mbox series

Message ID 1563758631-29550-9-git-send-email-jsimmons@infradead.org
State New
Headers show
Series
  • ldiskfs patches against 5.2-rc2+
Related show

Commit Message

James Simmons July 22, 2019, 1:23 a.m. UTC
Use struct dx_root_info directly.

Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 fs/ext4/namei.c | 110 +++++++++++++++++++++++++++++---------------------------
 1 file changed, 58 insertions(+), 52 deletions(-)

Comments

NeilBrown July 22, 2019, 4:52 a.m. UTC | #1
On Sun, Jul 21 2019, James Simmons wrote:

> Use struct dx_root_info directly.

This looks like a style change.
Instead of a 'struct' that models the start of an on-disk directory
block, the location of some fields is done using calculations instead.

Why would we want to do that?  Might we want dx_root_info to be at a
different offset in the directory ??

NeilBrown
Andreas Dilger July 23, 2019, 2:07 a.m. UTC | #2
This is needed so that we can add extra data to struct ext4_dir_entry
(Lustre FID) via the "dirdata" feature, and struct dx_root assumes "." and
".." entries are a fixed size.

So there is a reason for the patch, and I think it would be acceptable
upstream. Artem @ Cray has an updated version of this patch that
was submitted upstream to linux-ext4 and reviewed, but it needs to
be refreshed again. 

Cheers, Andreas

> On Jul 21, 2019, at 22:52, NeilBrown <neilb@suse.com> wrote:
> 
>> On Sun, Jul 21 2019, James Simmons wrote:
>> 
>> Use struct dx_root_info directly.
> 
> This looks like a style change.
> Instead of a 'struct' that models the start of an on-disk directory
> block, the location of some fields is done using calculations instead.
> 
> Why would we want to do that?  Might we want dx_root_info to be at a
> different offset in the directory ??
> 
> NeilBrown
Artem Blagodarenko Aug. 5, 2019, 7:31 a.m. UTC | #3
We need this for dirdata feature.

´╗┐On 22/07/2019, 07:52, "NeilBrown" <neilb@suse.com> wrote:

    On Sun, Jul 21 2019, James Simmons wrote:
    
    > Use struct dx_root_info directly.
    
    This looks like a style change.
    Instead of a 'struct' that models the start of an on-disk directory
    block, the location of some fields is done using calculations instead.
    
    Why would we want to do that?  Might we want dx_root_info to be at a
    different offset in the directory ??
    
    NeilBrown

Patch
diff mbox series

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index dd64a10..4c45570 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -197,23 +197,13 @@  struct dx_entry
  * dirent the two low bits of the hash version will be zero.  Therefore, the
  * hash version mod 4 should never be 0.  Sincerely, the paranoia department.
  */
-
-struct dx_root
+struct dx_root_info
 {
-	struct fake_dirent dot;
-	char dot_name[4];
-	struct fake_dirent dotdot;
-	char dotdot_name[4];
-	struct dx_root_info
-	{
-		__le32 reserved_zero;
-		u8 hash_version;
-		u8 info_length; /* 8 */
-		u8 indirect_levels;
-		u8 unused_flags;
-	}
-	info;
-	struct dx_entry	entries[0];
+	__le32 reserved_zero;
+	u8 hash_version;
+	u8 info_length; /* 8 */
+	u8 indirect_levels;
+	u8 unused_flags;
 };
 
 struct dx_node
@@ -514,6 +504,16 @@  static inline int ext4_handle_dirty_dx_node(handle_t *handle,
  * Future: use high four bits of block for coalesce-on-delete flags
  * Mask them off for now.
  */
+struct dx_root_info *dx_get_dx_info(struct ext4_dir_entry_2 *de)
+{
+	/* get dotdot first */
+	de = (struct ext4_dir_entry_2 *)((char *)de + EXT4_DIR_REC_LEN(1));
+
+	/* dx root info is after dotdot entry */
+	de = (struct ext4_dir_entry_2 *)((char *)de + EXT4_DIR_REC_LEN(2));
+
+	return (struct dx_root_info *)de;
+}
 
 static inline ext4_lblk_t dx_get_block(struct dx_entry *entry)
 {
@@ -738,7 +738,7 @@  struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
 {
 	unsigned count, indirect;
 	struct dx_entry *at, *entries, *p, *q, *m;
-	struct dx_root *root;
+	struct dx_root_info *info;
 	struct dx_frame *frame = frame_in;
 	struct dx_frame *ret_err = ERR_PTR(ERR_BAD_DX_DIR);
 	u32 hash;
@@ -748,17 +748,17 @@  struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
 	if (IS_ERR(frame->bh))
 		return (struct dx_frame *) frame->bh;
 
-	root = (struct dx_root *) frame->bh->b_data;
-	if (root->info.hash_version != DX_HASH_TEA &&
-	    root->info.hash_version != DX_HASH_HALF_MD4 &&
-	    root->info.hash_version != DX_HASH_LEGACY) {
+	info = dx_get_dx_info((struct ext4_dir_entry_2 *)frame->bh->b_data);
+	if (info->hash_version != DX_HASH_TEA &&
+	    info->hash_version != DX_HASH_HALF_MD4 &&
+	    info->hash_version != DX_HASH_LEGACY) {
 		ext4_warning_inode(dir, "Unrecognised inode hash code %u for directory %lu",
-				   root->info.hash_version, dir->i_ino);
+				   info->hash_version, dir->i_ino);
 		goto fail;
 	}
 	if (fname)
 		hinfo = &fname->hinfo;
-	hinfo->hash_version = root->info.hash_version;
+	hinfo->hash_version = info->hash_version;
 	if (hinfo->hash_version <= DX_HASH_TEA)
 		hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
@@ -766,13 +766,13 @@  struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
 		ext4fs_dirhash(dir, fname_name(fname), fname_len(fname), hinfo);
 	hash = hinfo->hash;
 
-	if (root->info.unused_flags & 1) {
+	if (info->unused_flags & 1) {
 		ext4_warning_inode(dir, "Unimplemented hash flags: %#06x",
-				   root->info.unused_flags);
+				   info->unused_flags);
 		goto fail;
 	}
 
-	indirect = root->info.indirect_levels;
+	indirect = info->indirect_levels;
 	if (indirect >= ext4_dir_htree_level(dir->i_sb)) {
 		ext4_warning(dir->i_sb,
 			     "Directory (ino: %lu) htree depth %#06x exceed"
@@ -785,14 +785,13 @@  struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
 		goto fail;
 	}
 
-	entries = (struct dx_entry *)(((char *)&root->info) +
-				      root->info.info_length);
+	entries = (struct dx_entry *)(((char *)info) + info->info_length);
 
 	if (dx_get_limit(entries) != dx_root_limit(dir,
-						   root->info.info_length)) {
+						   info->info_length)) {
 		ext4_warning_inode(dir, "dx entry: limit %u != root limit %u",
 				   dx_get_limit(entries),
-				   dx_root_limit(dir, root->info.info_length));
+				   dx_root_limit(dir, info->info_length));
 		goto fail;
 	}
 
@@ -877,7 +876,7 @@  static void dx_release(struct dx_frame *frames)
 	if (frames[0].bh == NULL)
 		return;
 
-	info = &((struct dx_root *)frames[0].bh->b_data)->info;
+	info = dx_get_dx_info((struct ext4_dir_entry_2 *)frames[0].bh->b_data);
 	/* save local copy, "info" may be freed after brelse() */
 	indirect_levels = info->indirect_levels;
 	for (i = 0; i <= indirect_levels; i++) {
@@ -2020,17 +2019,16 @@  static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 			    struct inode *inode, struct buffer_head *bh)
 {
 	struct buffer_head *bh2;
-	struct dx_root	*root;
 	struct dx_frame	frames[EXT4_HTREE_LEVEL], *frame;
 	struct dx_entry *entries;
-	struct ext4_dir_entry_2	*de, *de2;
+	struct ext4_dir_entry_2	*de, *de2, *dot_de, *dotdot_de;
 	struct ext4_dir_entry_tail *t;
 	char		*data1, *top;
 	unsigned	len;
 	int		retval;
 	unsigned	blocksize;
 	ext4_lblk_t  block;
-	struct fake_dirent *fde;
+	struct dx_root_info *dx_info;
 	int csum_size = 0;
 
 	if (ext4_has_metadata_csum(inode->i_sb))
@@ -2045,18 +2043,19 @@  static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 		brelse(bh);
 		return retval;
 	}
-	root = (struct dx_root *) bh->b_data;
+
+	dot_de = (struct ext4_dir_entry_2 *)bh->b_data;
+	dotdot_de = ext4_next_entry(dot_de, blocksize);
 
 	/* The 0th block becomes the root, move the dirents out */
-	fde = &root->dotdot;
-	de = (struct ext4_dir_entry_2 *)((char *)fde +
-		ext4_rec_len_from_disk(fde->rec_len, blocksize));
-	if ((char *) de >= (((char *) root) + blocksize)) {
+	de = (struct ext4_dir_entry_2 *)((char *)dotdot_de +
+		ext4_rec_len_from_disk(dotdot_de->rec_len, blocksize));
+	if ((char *)de >= (((char *)dot_de) + blocksize)) {
 		EXT4_ERROR_INODE(dir, "invalid rec_len for '..'");
 		brelse(bh);
 		return -EFSCORRUPTED;
 	}
-	len = ((char *) root) + (blocksize - csum_size) - (char *) de;
+	len = ((char *)dot_de) + (blocksize - csum_size) - (char *) de;
 
 	/* Allocate new block for the 0th block's dirents */
 	bh2 = ext4_append(handle, dir, &block);
@@ -2082,19 +2081,24 @@  static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 	}
 
 	/* Initialize the root; the dot dirents already exist */
-	de = (struct ext4_dir_entry_2 *) (&root->dotdot);
-	de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2),
-					   blocksize);
-	memset (&root->info, 0, sizeof(root->info));
-	root->info.info_length = sizeof(root->info);
-	root->info.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
-	entries = root->entries;
+	dotdot_de->rec_len =
+		ext4_rec_len_to_disk(blocksize - le16_to_cpu(dot_de->rec_len),
+				     blocksize);
+
+	/* initialize hashing info */
+	dx_info = dx_get_dx_info(dot_de);
+	memset(dx_info, 0, sizeof(*dx_info));
+	dx_info->info_length = sizeof(*dx_info);
+	dx_info->hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
+
+	entries = (void *)dx_info + sizeof(*dx_info);
+
 	dx_set_block(entries, 1);
 	dx_set_count(entries, 1);
-	dx_set_limit(entries, dx_root_limit(dir, sizeof(root->info)));
+	dx_set_limit(entries, dx_root_limit(dir, sizeof(*dx_info)));
 
 	/* Initialize as for dx_probe */
-	fname->hinfo.hash_version = root->info.hash_version;
+	fname->hinfo.hash_version = dx_info->hash_version;
 	if (fname->hinfo.hash_version <= DX_HASH_TEA)
 		fname->hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	fname->hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
@@ -2443,7 +2447,8 @@  static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
 				goto journal_error;
 			}
 		} else {
-			struct dx_root *dxroot;
+			struct dx_root_info *info;
+
 			memcpy((char *) entries2, (char *) entries,
 			       icount * sizeof(struct dx_entry));
 			dx_set_limit(entries2, dx_node_limit(dir));
@@ -2451,8 +2456,9 @@  static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
 			/* Set up root */
 			dx_set_count(entries, 1);
 			dx_set_block(entries + 0, newblock);
-			dxroot = (struct dx_root *)frames[0].bh->b_data;
-			dxroot->info.indirect_levels += 1;
+			info = dx_get_dx_info((struct ext4_dir_entry_2 *)
+					      frames[0].bh->b_data);
+			info->indirect_levels += 1;
 			dxtrace(printk(KERN_DEBUG
 				       "Creating %d level index...\n",
 				       dxroot->info.indirect_levels));