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Date: Wed, 19 Mar 2014 15:59:54 +0100 (CET)
From: Lukáš Czerner <lczerner@...hat.com>
To: Lubos Uhliarik <uhliarik@...nam.cz>
cc: Andreas Dilger <adilger@...ger.ca>, linux-ext4@...r.kernel.org,
vojnar@....vutbr.cz
Subject: Re: [RFC][PATCH 1/1] ext4: Undelete Feature for Ext4
On Wed, 19 Mar 2014, Lubos Uhliarik wrote:
> 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.
Hi Lubos,
you should definitely put some description into PATCH 1/1 as well -
that's what will eventually end up in the git repository and it
should contain description so that people know what it is all about.
Having e2fsprogs debugfs undelete command is actually a very good
idea. But I think this should be very easy to do with your current
program, or in addition to what you currently have since you're
already using ext2fs library.
Thanks!
-Lukas
>
> 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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