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Message-ID: <1395237544.15587.15.camel@zerobox.home>
Date: Wed, 19 Mar 2014 14:59:04 +0100
From: Lubos Uhliarik <uhliarik@...nam.cz>
To: Andreas Dilger <adilger@...ger.ca>
Cc: linux-ext4@...r.kernel.org, vojnar@....vutbr.cz,
lczerner@...hat.com
Subject: Re: [RFC][PATCH 1/1] ext4: Undelete Feature for Ext4
Hi Andreas,
maybe you didn't notice, but I sent comments in email with subject
"[RFC][PATCH 0/1] ext4: Undelete Feature for Ext4". Maybe, I should
mention this in [PATCH 1/1]. In this mail is also link to git repository
with undelete app (uses ext2fslibs), which demonstrates how to undelete
file with changes in kernel.
I hope, it will help you.
Regards,
Lubos
Andreas Dilger píše v Út 18. 03. 2014 v 12:23 -0600:
> On Mar 18, 2014, at 9:09 AM, Lubos Uhliarik <uhliarik@...nam.cz> wrote:
> > This patch should make undelete process for deleted files under ext4 fs easier.
>
> Hi Lubos,
> thanks for the interesting patch. This does seem like an improvement.
> It would be good to add more description to your commit comment, since
> it should explain what is actually being done in your patch (e.g. store
> the extent count and depth in the ext4_extent_header eh_generation field,
> ...).
>
> It would also be good to include a matching patch for e2fsprogs debugfs
> in the "undelete" command. I think one obstacle is the fact that inodes
> have their blocks zeroed out by the kernel during truncation. It would
> be necessary to change the kernel slightly to avoid writing out i_blocks
> with zero if the inode is being deleted. Otherwise, this change is not
> as useful as it could be.
>
> Cheers, Andreas
>
> > 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
> >
> >
> >
> >
> >
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
> Cheers, Andreas
>
>
>
>
>
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