On Tue, Jan 16, 2018 at 12:10 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > On Tue, Jan 16, 2018 at 10:37 AM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: >> On Tue, Jan 16, 2018 at 11:16 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: >>> On Thu, Jan 4, 2018 at 6:20 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: >>>> Lookup overlay inode in cache by origin inode, so we can decode a file >>>> handle of an open file even if the index has a whiteout index entry to >>>> mark this overlay inode was unlinked. >>>> >>>> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> >>>> --- >>>> fs/overlayfs/export.c | 22 ++++++++++++++++++++-- >>>> fs/overlayfs/inode.c | 16 ++++++++++++++++ >>>> fs/overlayfs/overlayfs.h | 1 + >>>> 3 files changed, 37 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c >>>> index 602bada474ba..6ecb54d4b52c 100644 >>>> --- a/fs/overlayfs/export.c >>>> +++ b/fs/overlayfs/export.c >>>> @@ -385,13 +385,21 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb, >>>> struct ovl_path *stack = &origin; >>>> struct dentry *dentry = NULL; >>>> struct dentry *index = NULL; >>>> + struct inode *inode = NULL; >>>> + bool is_deleted = false; >>>> int err; >>>> >>>> /* First lookup indexed upper by fh */ >>> >>> Why not first look up origin, then look up ovl inode by origin? It >>> seems a faster path than going through the index first. Obviously if >>> icache lookup fails then we need to look up index, but the common case >>> will the cached one, so that should be the fast one, no? >>> >> >> Not really, because we do not know if the file handle is dir or non-dir. >> If file handle is dir than decode of file handle is expensive and can >> reduce worst case from two file handle decodes to just one: >> >> For lower dir: >> - one index lookup fails >> - one lower dir decode >> - one icache lookup >> - maybe one ovl_lookup_real(is_upper=false) >> >> For copied up indexed dir: >> - one index lookup success >> - one upper dir decode >> - one ovl_lookup_real(is_upper=true) >> >> That method avoids the origin dir decode for upper indexed >> dir at the cost of not looking for the decoded dir in icache. >> >> How about this as in idea: hash overlay inodes for NFS export >> by origin fh instead of by origin inode pointer. > > Good idea. That way we can leave out the middleman (underlying fh > decode) in the cached case. > If it's all right with you, I prefer to get the initial version out the door first and handle this optimization later. Shout if you disagree. Thanks, Amir.
