[PATCH v6 0/4] nvmet: avoid recursive configfs open

[Runyu Xiao]

Several configfs store callbacks open user-configured paths while holding
the item's frag_sem.  If a configured path resolves into configfs, the open
can re-enter __configfs_open_file() and try to acquire the same
non-recursive semaphore again.

Add helpers in configfs for opening non-configfs paths, then use them in the
nvmet file-backed namespace and passthru paths.  The series also pins the
target-core db_root path and uses the root-relative helper for ALUA and APTPL
metadata, so the helper has its target-core consumer in the same series.

Changes since v5:
- Add the target-core db_root patch as 4/4 and use configfs_open_root() for
  validation and metadata opens.
- Replace the verbose helper kerneldoc with concise interface descriptions.
- Keep the Reviewed-by tags on the unchanged nvmet patches.

Runyu Xiao (4):
  fs: configfs: add helpers for opening non-configfs paths
  nvmet: avoid recursive configfs open for file-backed namespaces
  nvmet: avoid recursive configfs open for passthru
  scsi: target: pin db_root for metadata writes

 drivers/nvme/target/io-cmd-file.c     |   3 +-
 drivers/nvme/target/passthru.c        |   3 +-
 drivers/target/target_core_alua.c     |  42 +++++-----
 drivers/target/target_core_configfs.c | 116 ++++++++++++++++++++------
 drivers/target/target_core_internal.h |   3 +
 drivers/target/target_core_pr.c       |  21 +++--
 fs/configfs/mount.c                   |  53 ++++++++++++
 include/linux/configfs.h              |   5 ++
 8 files changed, 189 insertions(+), 57 deletions(-)


base-commit: df2908090cda368b01ff43709f51890076c56157
-- 
2.34.1