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author | Al Viro <viro@zeniv.linux.org.uk> | 2018-05-16 16:55:01 +0200 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2018-06-28 21:28:48 +0200 |
commit | b0c6108ecf64fce3987f80c1610472a56d480d9a (patch) | |
tree | f02a6116f9c95eb0f560a8784ab670e95d1c1382 /fs/fuse | |
parent | proc: add proc_seq_release (diff) | |
download | linux-b0c6108ecf64fce3987f80c1610472a56d480d9a.tar.xz linux-b0c6108ecf64fce3987f80c1610472a56d480d9a.zip |
nfs_instantiate(): prevent multiple aliases for directory inode
Since NFS allows open-by-fhandle, we have to cope with the possibility
of mkdir vs. open-by-guessed-handle races. A local filesystem could
decide what the inumber of the new object will be and insert a locked
inode with that inumber into icache _before_ the on-disk data structures
begin to look good and unlock it only once it has a dentry alias, so
that open-by-handle coming first would quietly fail and mkdir coming
first would have open-by-handle grab its dentry.
For NFS it's a non-starter - the icache key is server-supplied fhandle
and we do not get that until the object has been fully created on server.
We really have to deal with the possibility that open-by-handle gets
the in-core inode and attaches a dentry to it before mkdir does.
Solution: let nfs_mkdir() use d_splice_alias() to catch those. We can
* get an error. Just return it to our caller.
* get NULL - no preexisting dentry aliases, we'd just done what
d_add() would've done. Success.
* get a reference to preexisting alias. In that case the alias
had been moved in place of nfs_mkdir() argument (and hashed there), while
nfs_mkdir() argument is left unhashed negative. Which is just fine for
->mkdir() callers, all we need is to release the reference we'd got from
d_splice_alias() and report success.
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/fuse')
0 files changed, 0 insertions, 0 deletions