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Message-Id: <200908221620.50103.schlick@lavabit.com>
Date: Sat, 22 Aug 2009 16:20:49 +0200
From: Andreas Schlick <schlick@...abit.com>
To: Theodore Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: [PATCH 1/1] dir shrink (was Re: ext3/ext4 directories don't shrink after deleting lots of files)
Hello,
> Anyway, if there's someone interested in trying to implement this,
> give me a holler; I'd be happy to give more details as necessary.
I'd like to try it. It looks like a nice starting project.
Following your outline the first version of the patch tries to remove an empty
block at the end of a non-htree directory. I'd appreciate it if you checked it
and gave me suggestions for improving it.
At the moment I am looking at the dir_index code, so I can extend it to htree
directories. Please let me know if you want me to port it to ext3, although
personally I think it is better to do so at later point.
Greetings Andreas
[PATCH] ext4: Add a function to shrink directories by removing last empty block.
Current limitations: It only works on directories that don't use htree and will
only remove the last block (if it is not used).
Signed-off-by: Andreas Schlick <schlick@...abit.com>
---
fs/ext4/namei.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 65 insertions(+), 5 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 1855060..04ac43d 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -79,6 +79,13 @@ static struct buffer_head *ext4_append(handle_t *handle,
#define dxtrace(command)
#endif
+// ext4_dir_cleanup holds information for ext4_shrink_directory(..).
+// At the moment it is only a pointer to the directory's inode but this
+// will change in later versions of the patch.
+struct ext4_dir_cleanup {
+ struct inode *dir;
+};
+
struct fake_dirent
{
__le32 inode;
@@ -1684,7 +1691,8 @@ cleanup:
static int ext4_delete_entry(handle_t *handle,
struct inode *dir,
struct ext4_dir_entry_2 *de_del,
- struct buffer_head *bh)
+ struct buffer_head *bh,
+ struct ext4_dir_cleanup *dc)
{
struct ext4_dir_entry_2 *de, *pde;
unsigned int blocksize = dir->i_sb->s_blocksize;
@@ -1711,6 +1719,9 @@ static int ext4_delete_entry(handle_t *handle,
dir->i_version++;
BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
ext4_handle_dirty_metadata(handle, dir, bh);
+ if (dc) {
+ dc->dir = dir;
+ }
return 0;
}
i += ext4_rec_len_from_disk(de->rec_len, blocksize);
@@ -1989,6 +2000,49 @@ static int empty_dir(struct inode *inode)
return 1;
}
+/*
+ * This function tries to shrink the size of a directory.
+ *
+ * The current limitations are that it checks only the last block
+ * and only works on non-indexed directories.
+ */
+static void ext4_shrink_directory(struct ext4_dir_cleanup *dc) {
+ struct inode *dir = dc->dir;
+ struct buffer_head *bh;
+ struct ext4_dir_entry_2 * de;
+ char * dlimit;
+ ext4_lblk_t lblock;
+ int err=0;
+
+ lblock = dir->i_size >> EXT4_BLOCK_SIZE_BITS(dir->i_sb);
+
+ // We don't handle indexed dirs at the moment and need at least two blocks
+ if (is_dx(dir) || lblock <= 1) {
+ return;
+ }
+
+ bh = ext4_bread(NULL, dir, (lblock-1), 0, &err);
+
+ if (!bh) {
+ return;
+ }
+
+ de = (struct ext4_dir_entry_2 *) bh->b_data;
+ dlimit = bh->b_data + dir->i_sb->s_blocksize;
+ while ((char *) de < dlimit) {
+ if (de->inode) {
+ brelse(bh);
+ return;
+ }
+ de = ext4_next_entry(de, EXT4_BLOCK_SIZE(dir->i_sb));
+ }
+
+ brelse(bh);
+
+ dir->i_size -= EXT4_BLOCK_SIZE(dir->i_sb);
+ ext4_truncate(dir);
+}
+
/* ext4_orphan_add() links an unlinked or truncated inode into a list of
* such inodes, starting at the superblock, in case we crash before the
* file is closed/deleted, or in case the inode truncate spans multiple
@@ -2145,6 +2199,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
struct inode *inode;
struct buffer_head *bh;
struct ext4_dir_entry_2 *de;
+ struct ext4_dir_cleanup dc;
handle_t *handle;
/* Initialize quotas before so that eventual writes go in
@@ -2172,7 +2227,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
if (!empty_dir(inode))
goto end_rmdir;
- retval = ext4_delete_entry(handle, dir, de, bh);
+ retval = ext4_delete_entry(handle, dir, de, bh, &dc);
if (retval)
goto end_rmdir;
if (!EXT4_DIR_LINK_EMPTY(inode))
@@ -2195,6 +2250,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
end_rmdir:
ext4_journal_stop(handle);
brelse(bh);
+ ext4_shrink_directory(&dc);
return retval;
}
@@ -2204,6 +2260,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
struct inode *inode;
struct buffer_head *bh;
struct ext4_dir_entry_2 *de;
+ struct ext4_dir_cleanup dc;
handle_t *handle;
/* Initialize quotas before so that eventual writes go
@@ -2233,7 +2290,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
inode->i_ino, inode->i_nlink);
inode->i_nlink = 1;
}
- retval = ext4_delete_entry(handle, dir, de, bh);
+ retval = ext4_delete_entry(handle, dir, de, bh, &dc);
if (retval)
goto end_unlink;
dir->i_ctime = dir->i_mtime = ext4_current_time(dir);
@@ -2249,6 +2306,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
end_unlink:
ext4_journal_stop(handle);
brelse(bh);
+ ext4_shrink_directory(&dc);
return retval;
}
@@ -2369,6 +2427,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *old_inode, *new_inode;
struct buffer_head *old_bh, *new_bh, *dir_bh;
struct ext4_dir_entry_2 *old_de, *new_de;
+ struct ext4_dir_cleanup dc;
int retval, force_da_alloc = 0;
old_bh = new_bh = dir_bh = NULL;
@@ -2459,7 +2518,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
old_de->name_len != old_dentry->d_name.len ||
strncmp(old_de->name, old_dentry->d_name.name, old_de->name_len) ||
(retval = ext4_delete_entry(handle, old_dir,
- old_de, old_bh)) == -ENOENT) {
+ old_de, old_bh, &dc)) == -ENOENT) {
/* old_de could have moved from under us during htree split, so
* make sure that we are deleting the right entry. We might
* also be pointing to a stale entry in the unused part of
@@ -2470,7 +2529,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
old_bh2 = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de2);
if (old_bh2) {
retval = ext4_delete_entry(handle, old_dir,
- old_de2, old_bh2);
+ old_de2, old_bh2, &dc);
brelse(old_bh2);
}
}
@@ -2519,6 +2578,7 @@ end_rename:
brelse(old_bh);
brelse(new_bh);
ext4_journal_stop(handle);
+ ext4_shrink_directory(&dc);
if (retval == 0 && force_da_alloc)
ext4_alloc_da_blocks(old_inode);
return retval;
--
1.6.4
--
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