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ovl: lookup indexed ancestor of lower dir

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ovl_lookup_real() in lower layer walks back lower parents to find the
topmost indexed parent. If an indexed ancestor is found before reaching
lower layer root, ovl_lookup_real() is called recursively with upper
layer to walk back from indexed upper to the topmost connected/hashed
upper parent (or up to root).

ovl_lookup_real() in upper layer then walks forward to connect the topmost
upper overlay dir dentry and ovl_lookup_real() in lower layer continues to
walk forward to connect the decoded lower overlay dir dentry.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein
2018-01-17 14:40:27 +02:00
committed by Miklos Szeredi
parent 4b91c30a5a
commit 0617015403
3 changed files with 56 additions and 7 deletions
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41
fs/overlayfs/export.c
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@@ -294,6 +294,10 @@ fail:
goto out;
}
static struct dentry *ovl_lookup_real(struct super_block *sb,
struct dentry *real,
struct ovl_layer *layer);
/*
* Lookup an indexed or hashed overlay dentry by real inode.
*/
@@ -301,9 +305,16 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
struct dentry *real,
struct ovl_layer *layer)
{
struct ovl_fs *ofs = sb->s_fs_info;
struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
struct dentry *index = NULL;
struct dentry *this = NULL;
struct inode *inode;
/*
* Decoding upper dir from index is expensive, so first try to lookup
* overlay dentry in inode/dcache.
*/
inode = ovl_lookup_inode(sb, real, !layer->idx);
if (IS_ERR(inode))
return ERR_CAST(inode);
@@ -312,7 +323,35 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
iput(inode);
}
/* TODO: use index when looking up by origin inode */
/*
* For decoded lower dir file handle, lookup index by origin to check
* if lower dir was copied up and and/or removed.
*/
if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
index = ovl_lookup_index(ofs, NULL, real, false);
if (IS_ERR(index))
return index;
}
/* Get connected upper overlay dir from index */
if (index) {
struct dentry *upper = ovl_index_upper(ofs, index);
dput(index);
if (IS_ERR_OR_NULL(upper))
return upper;
/*
* ovl_lookup_real() in lower layer may call recursively once to
* ovl_lookup_real() in upper layer. The first level call walks
* back lower parents to the topmost indexed parent. The second
* recursive call walks back from indexed upper to the topmost
* connected/hashed upper parent (or up to root).
*/
this = ovl_lookup_real(sb, upper, &upper_layer);
dput(upper);
}
if (!this)
return NULL;