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| author |   Amir Goldstein <amir73il@gmail.com> | 2018-03-09 15:51:02 +0200 |
|---|---|---|
| committer |   Miklos Szeredi <mszeredi@redhat.com> | 2018-04-12 12:04:49 +0200 |
| commit | 8a22efa15b46d524577cac79da63cebca8e8307f (patch) | |
| tree | d6c87569edb074ddd6edb3b88eb3105abefb3d6b /fs/exportfs | |
| parent | ovl: disambiguate ovl_encode_fh() (diff) | |
| download | linux-dev-8a22efa15b46d524577cac79da63cebca8e8307f.tar.xz linux-dev-8a22efa15b46d524577cac79da63cebca8e8307f.zip | |
ovl: do not try to reconnect a disconnected origin dentry
On lookup of non directory, we try to decode the origin file handle
stored in upper inode. The origin file handle is supposed to be decoded
to a disconnected non-dir dentry, which is fine, because we only need
the lower inode of a copy up origin.
However, if the origin file handle somehow turns out to be a directory
we pay the expensive cost of reconnecting the directory dentry, only to
get a mismatch file type and drop the dentry.
Optimize this case by explicitly opting out of reconnecting the dentry.
Opting-out of reconnect is done by passing a NULL acceptable callback
to exportfs_decode_fh().
While the case described above is a strange corner case that does not
really need to be optimized, the API added for this optimization will
be used by a following patch to optimize a more common case of decoding
an overlayfs file handle.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/exportfs')
| -rw-r--r-- | fs/exportfs/expfs.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index 329a5d103846..645158dc33f1 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -435,6 +435,15 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, if (IS_ERR_OR_NULL(result)) return ERR_PTR(-ESTALE); + /* + * If no acceptance criteria was specified by caller, a disconnected + * dentry is also accepatable. Callers may use this mode to query if + * file handle is stale or to get a reference to an inode without + * risking the high overhead caused by directory reconnect. + */ + if (!acceptable) + return result; + if (d_is_dir(result)) { /* * This request is for a directory. |