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Date:	Tue, 18 Mar 2014 16:09:44 +0100
From:	Lubos Uhliarik <uhliarik@...nam.cz>
To:	linux-ext4@...r.kernel.org
Cc:	vojnar@....vutbr.cz, lczerner@...hat.com
Subject: [RFC][PATCH 1/1] ext4: Undelete Feature for Ext4


This patch should make undelete process for deleted files under ext4 fs easier.

Signed-off-by: Lubos Uhliarik <uhliarik@...nam.cz>
---
 fs/ext4/ext4_extents.h | 14 +++++++++++
 fs/ext4/extents.c      | 67 +++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 75 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index 5074fe2..22cf2cd 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -251,6 +251,20 @@ static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
 				      0xffff);
 }
 
+static inline void ext4_ext_store_entries(struct ext4_extent_header *eh,
+					  __u16 eh_entries){
+	eh->eh_generation &= cpu_to_le32((unsigned long) 0x0000ffff);
+	eh->eh_generation |= cpu_to_le32(((unsigned long) (eh_entries) << 16)
+				& 0xffff0000);
+}
+
+static inline void ext4_ext_store_depth(struct ext4_extent_header *eh,
+					 __u16 eh_depth){
+	eh->eh_generation &= cpu_to_le32((unsigned long) 0xffff0000);
+	eh->eh_generation |= cpu_to_le32(((unsigned long) (eh_depth))
+				& 0x0000ffff);
+}
+
 /*
  * ext4_idx_store_pblock:
  * stores a large physical block number into an index struct,
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 74bc2d5..f0f3615 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2565,6 +2565,7 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
 	ext4_lblk_t ex_ee_block;
 	unsigned short ex_ee_len;
 	unsigned uninitialized = 0;
+	unsigned short ex_ee_entries;
 	struct ext4_extent *ex;
 	ext4_fsblk_t pblk;
 
@@ -2584,6 +2585,7 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
 
 	ex_ee_block = le32_to_cpu(ex->ee_block);
 	ex_ee_len = ext4_ext_get_actual_len(ex);
+	ex_ee_entries = le16_to_cpu(eh->eh_entries);
 
 	trace_ext4_ext_rm_leaf(inode, start, ex, *partial_cluster);
 
@@ -2662,11 +2664,9 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
 		if (err)
 			goto out;
 
-		if (num == 0)
-			/* this extent is removed; mark slot entirely unused */
-			ext4_ext_store_pblock(ex, 0);
+		if (num != 0)
+			ex->ee_len = cpu_to_le16(num);
 
-		ex->ee_len = cpu_to_le16(num);
 		/*
 		 * Do not mark uninitialized if all the blocks in the
 		 * extent have been removed.
@@ -2726,8 +2726,19 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
 
 	/* if this leaf is free, then we should
 	 * remove it from index block above */
-	if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL)
+	if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL) {
+		err = ext4_ext_get_access(handle, inode, path + depth);
+		if (err)
+			goto out;
+
+		ext4_ext_store_entries(path[depth].p_hdr, ex_ee_entries);
+
+		err = ext4_ext_dirty(handle, inode, path + depth);
+		if (err)
+			goto out;
+
 		err = ext4_ext_rm_idx(handle, inode, path, depth);
+	}
 
 out:
 	return err;
@@ -2760,6 +2771,7 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
 	struct super_block *sb = inode->i_sb;
 	int depth = ext_depth(inode);
 	struct ext4_ext_path *path = NULL;
+	unsigned short *entries_path = NULL;
 	long long partial_cluster = 0;
 	handle_t *handle;
 	int i = 0, err = 0;
@@ -2864,6 +2876,18 @@ again:
 	}
 	err = 0;
 
+	if (!inode->i_nlink) {
+		entries_path = kzalloc(sizeof(short) * (depth + 1),
+				       GFP_NOFS);
+		if (entries_path == NULL) {
+			kfree(path);
+			ext4_journal_stop(handle);
+			return -ENOMEM;
+		}
+
+		entries_path[0] = le16_to_cpu(ext_inode_hdr(inode)->eh_entries);
+	}
+
 	while (i >= 0 && err == 0) {
 		if (i == depth) {
 			/* this is leaf block */
@@ -2890,6 +2914,10 @@ again:
 			ext_debug("init index ptr: hdr 0x%p, num %d\n",
 				  path[i].p_hdr,
 				  le16_to_cpu(path[i].p_hdr->eh_entries));
+			if (entries_path != NULL) {
+				entries_path[i] = le16_to_cpu(
+					path[i].p_hdr->eh_entries);
+			}
 		} else {
 			/* we were already here, see at next index */
 			path[i].p_idx--;
@@ -2928,10 +2956,24 @@ again:
 		} else {
 			/* we finished processing this index, go up */
 			if (path[i].p_hdr->eh_entries == 0 && i > 0) {
+				if (entries_path != NULL) {
+					err = ext4_ext_get_access(handle,
+						inode, path);
+					if (err == 0) {
+						ext4_ext_store_entries(
+							path[i].p_hdr,
+							(entries_path[i]));
+						err = ext4_ext_dirty(handle,
+							inode, path);
+					}
+				}
+
 				/* index is empty, remove it;
 				 * handle must be already prepared by the
 				 * truncatei_leaf() */
-				err = ext4_ext_rm_idx(handle, inode, path, i);
+				if (err == 0)
+					err = ext4_ext_rm_idx(handle, inode,
+						path, i);
 			}
 			/* root level has p_bh == NULL, brelse() eats this */
 			brelse(path[i].p_bh);
@@ -2964,6 +3006,17 @@ again:
 		 */
 		err = ext4_ext_get_access(handle, inode, path);
 		if (err == 0) {
+			/* Store depth and entries to eh_generation to make
+			 * recovering deleted files easier. */
+			if (entries_path != NULL) {
+				ext4_ext_store_entries(ext_inode_hdr(inode),
+					(entries_path[0]));
+
+				ext4_ext_store_depth(ext_inode_hdr(inode),
+					le16_to_cpu(
+					ext_inode_hdr(inode)->eh_depth));
+			}
+
 			ext_inode_hdr(inode)->eh_depth = 0;
 			ext_inode_hdr(inode)->eh_max =
 				cpu_to_le16(ext4_ext_space_root(inode, 0));
@@ -2973,6 +3026,8 @@ again:
 out:
 	ext4_ext_drop_refs(path);
 	kfree(path);
+	kfree(entries_path);
+
 	if (err == -EAGAIN) {
 		path = NULL;
 		goto again;
-- 
1.8.3.2







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