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staging: lustre: llite: Trust creates in revalidate too.

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By forcing creates to always go via lookup we lose some
important caching benefits too.
Instead let's trust creates with positive cached entries.

Then we have 3 possible outcomes:
1. Negative dentry - we go via atomic_open and do the create
   by name there.
2. Positive dentry, no contention - we just go straight to
   ll_intent_file_open and open by fid.
3. positive dentry, contention - by the time we reach the server,
   the inode is gone. We get ENOENT which is unacceptable to return
   from create. But since we know it's a create, we substitute it
   with ESTALE and VFS retries again with LOOKUP_REVAL set, we catch
   that in revalidate and force a lookup (same path as before this
   patch).

Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8371
Reviewed-on: http://review.whamcloud.com/21168
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oleg Drokin 2017-01-28 19:04:54 -05:00 committed by Greg Kroah-Hartman
parent e27bcd66cb
commit d9421ff6c1
2 changed files with 16 additions and 8 deletions
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13
drivers/staging/lustre/lustre/llite/dcache.c
View File

@ -247,17 +247,14 @@ static int ll_revalidate_dentry(struct dentry *dentry,
return 1;
/*
* if open&create is set, talk to MDS to make sure file is created if
* necessary, because we can't do this in ->open() later since that's
* called on an inode. return 0 here to let lookup to handle this.
* VFS warns us that this is the second go around and previous
* operation failed (most likely open|creat), so this time
* we better talk to the server via the lookup path by name,
* not by fid.
*/
if ((lookup_flags & (LOOKUP_OPEN | LOOKUP_CREATE)) ==
(LOOKUP_OPEN | LOOKUP_CREATE))
if (lookup_flags & LOOKUP_REVAL)
return 0;
if (lookup_flags & (LOOKUP_PARENT | LOOKUP_OPEN | LOOKUP_CREATE))
return 1;
if (!dentry_may_statahead(dir, dentry))
return 1;

11
drivers/staging/lustre/lustre/llite/file.c
View File

@ -417,6 +417,17 @@ out:
ptlrpc_req_finished(req);
ll_intent_drop_lock(itp);
/*
* We did open by fid, but by the time we got to the server,
* the object disappeared. If this is a create, we cannot really
* tell the userspace that the file it was trying to create
* does not exist. Instead let's return -ESTALE, and the VFS will
* retry the create with LOOKUP_REVAL that we are going to catch
* in ll_revalidate_dentry() and use lookup then.
*/
if (rc == -ENOENT && itp->it_op & IT_CREAT)
rc = -ESTALE;
return rc;
}