From: Theodore Ts'o <tytso@mit.edu>
Date: Tue, 20 May 2025 02:07:55 +0000 (-0400)
Subject: libext2fs: add the EXT2FS_LINK_APPEND flag to ext2fs_link()
X-Git-Tag: v1.47.3-rc1~74
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=53aa6c54224f545756da312e8756576dbaabe08a;p=thirdparty%2Fe2fsprogs.git

libext2fs: add the EXT2FS_LINK_APPEND flag to ext2fs_link()

Add a flag which only tries to add the new directory entry to the last
block in the directory.  This is helpful avoids mke2fs -d offering
from an O(n**2) performance bottleneck when adding a large number of
files to a directory.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 80310b29..2d5d1fdc 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -794,6 +794,20 @@ struct ext2_xattr_handle;
 #define EXT2FS_BITMAPS_INODE		0x0004
 #define EXT2FS_BITMAPS_VALID_FLAGS	0x0007
 
+/*
+ * flags for ext2fs_unlink()
+ */
+
+/* Forcefully unlink even if the inode number doesn't match the dirent */
+#define EXT2FS_UNLINK_FORCE		0x1
+
+/*
+ * flags for ext2fs_link()
+ *
+ */
+#define EXT2FS_LINK_FT_MASK	0x0007
+#define EXT2FS_LINK_APPEND	0x0010
+
 /*
  * function prototypes
  */
@@ -1816,10 +1830,6 @@ extern errcode_t ext2fs_get_pathname(ext2_filsys fs, ext2_ino_t dir, ext2_ino_t
 			       char **name);
 
 /* link.c */
-#define EXT2FS_UNLINK_FORCE		0x1	/* Forcefully unlink even if
-						 * the inode number doesn't
-						 * match the dirent
-						 */
 errcode_t ext2fs_link(ext2_filsys fs, ext2_ino_t dir, const char *name,
 		      ext2_ino_t ino, int flags);
 errcode_t ext2fs_unlink(ext2_filsys fs, ext2_ino_t dir, const char *name,
diff --git a/lib/ext2fs/link.c b/lib/ext2fs/link.c
index d69b1e3d..7ea00f82 100644
--- a/lib/ext2fs/link.c
+++ b/lib/ext2fs/link.c
@@ -254,7 +254,8 @@ static int link_proc(ext2_ino_t dir EXT2FS_ATTR((unused)),
 	ext2fs_dirent_set_name_len(dirent, ls->namelen);
 	strncpy(dirent->name, ls->name, ls->namelen);
 	if (ext2fs_has_feature_filetype(ls->sb))
-		ext2fs_dirent_set_file_type(dirent, ls->flags & 0x7);
+		ext2fs_dirent_set_file_type(dirent,
+					    ls->flags & EXT2FS_LINK_FT_MASK);
 
 	ls->done++;
 	return DIRENT_ABORT|DIRENT_CHANGED;
@@ -633,8 +634,34 @@ errcode_t ext2fs_link(ext2_filsys fs, ext2_ino_t dir, const char *name,
 	ls.blocksize = fs->blocksize;
 	ls.err = 0;
 
-	retval = ext2fs_dir_iterate2(fs, dir, DIRENT_FLAG_INCLUDE_EMPTY,
-				     NULL, link_proc, &ls);
+	if ((flags & EXT2FS_LINK_APPEND) &&
+	    !(inode.i_flags & EXT4_INLINE_DATA_FL)) {
+		blk64_t		lblk, pblk = 0;
+		struct dir_context ctx;
+
+		lblk = (inode.i_size / fs->blocksize) - 1;
+		retval = ext2fs_bmap2(fs, ino, &inode, NULL, 0, lblk,
+				      NULL, &pblk);
+		if (retval)
+			return retval;
+
+		ctx.dir = dir;
+		ctx.flags = flags;
+		ctx.func = link_proc;
+		ctx.priv_data = &ls;
+		ctx.errcode = 0;
+		retval = ext2fs_get_mem(fs->blocksize, &ctx.buf);
+		if (retval)
+			return retval;
+
+		ext2fs_process_dir_block(fs, &pblk, lblk, 0, 0, &ctx);
+		retval = ctx.errcode;
+		ext2fs_free_mem(&ctx.buf);
+	} else {
+		retval = ext2fs_dir_iterate2(fs, dir,
+					     DIRENT_FLAG_INCLUDE_EMPTY,
+					     NULL, link_proc, &ls);
+	}
 	if (retval)
 		return retval;
 	if (ls.err)