configfs: Introduce configfs_dirent_lock

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This patch introduces configfs_dirent_lock spinlock to protect configfs_dirent
traversals against linkage mutations (add/del/move). This will allow
configfs_detach_prep() to avoid locking i_mutexes.

Locking rules for configfs_dirent linkage mutations are the same plus the
requirement of taking configfs_dirent_lock. For configfs_dirent walking, one can
either take appropriate i_mutex as before, or take configfs_dirent_lock.

The spinlock could actually be a mutex, but the critical sections are either
O(1) or should not be too long (default groups walking in last patch).

ChangeLog:
  - Clarify the comment on configfs_dirent_lock usage
  - Move sd->s_element init before linking the new dirent
  - In lseek(), do not release configfs_dirent_lock before the dirent is
    relinked.

Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

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This commit is contained in:

Louis Rilling 2008-06-16 19:00:58 +02:00 • committed by Mark Fasheh

parent fe9f387740

commit 6f61076406

4 changed files with 34 additions and 1 deletions

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3

fs/configfs/configfs_internal.h

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28

fs/configfs/dir.c

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2

fs/configfs/inode.c

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2

fs/configfs/symlink.c

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