ovl: do not try to reconnect a disconnected origin dentry

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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>

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This commit is contained in:

Amir Goldstein 2018-03-09 15:51:02 +02:00 • committed by Miklos Szeredi

parent 5b2cccd32c

commit 8a22efa15b

4 changed files with 23 additions and 11 deletions

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9

fs/exportfs/expfs.c

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4

fs/overlayfs/export.c

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16

fs/overlayfs/namei.c

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5

fs/overlayfs/overlayfs.h

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