*
* We must take lli_trunc_sem in read mode on entry in to various i/o paths
* in Lustre, in order to exclude truncates. Some of these paths then need to
- * take the mmap_sem, while still holding the trunc_sem. The problem is that
- * page faults hold the mmap_sem when calling in to Lustre, and then must also
+ * take the mmap_lock, while still holding the trunc_sem. The problem is that
+ * page faults hold the mmap_lock when calling in to Lustre, and then must also
* take the trunc_sem to exclude truncate.
*
- * This means the locking order for trunc_sem and mmap_sem is sometimes AB,
+ * This means the locking order for trunc_sem and mmap_lock is sometimes AB,
* sometimes BA. This is almost OK because in both cases, we take the trunc
* sem for read, so it doesn't block.
*
*
* So we have, on our truncate sem, in order (where 'reader' and 'writer' refer
* to the mode in which they take the semaphore):
- * reader (holding mmap_sem, needs truncate_sem)
+ * reader (holding mmap_lock, needs truncate_sem)
* writer
- * reader (holding truncate sem, waiting for mmap_sem)
+ * reader (holding truncate sem, waiting for mmap_lock)
*
* And so the readers deadlock.
*
* of the order they arrived in.
*
* down_read_nowait is only used in the page fault case, where we already hold
- * the mmap_sem. This is because otherwise repeated read and write operations
+ * the mmap_lock. This is because otherwise repeated read and write operations
* (which take the truncate sem) could prevent a truncate from ever starting.
* This could still happen with page faults, but without an even more complex
* mechanism, this is unavoidable.
git://git.whamcloud.com / fs / lustre-release.git / blobdiff