修改led为gpio

hc

2024-10-12 a5969cabbb4660eab42b6ef0412cbbd1200cf14d

 kernel/Documentation/filesystems/directory-locking.rst
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 3) object removal.  Locking rules: caller locks parent, finds victim,
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 locks victim and calls the method.  Locks are exclusive.
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-4) rename() that is _not_ cross-directory.  Locking rules: caller locks
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-the parent and finds source and target.  In case of exchange (with
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-RENAME_EXCHANGE in flags argument) lock both.  In any case,
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-if the target already exists, lock it.  If the source is a non-directory,
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-lock it.  If we need to lock both, lock them in inode pointer order.
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-Then call the method.  All locks are exclusive.
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+4) rename() that is _not_ cross-directory.  Locking rules: caller locks the
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+parent and finds source and target.  We lock both (provided they exist).  If we
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+need to lock two inodes of different type (dir vs non-dir), we lock directory
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+first.  If we need to lock two inodes of the same type, lock them in inode
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+pointer order.  Then call the method.  All locks are exclusive.
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 NB: we might get away with locking the source (and target in exchange
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 case) shared.
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@@ -44,15 +43,17 @@
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 rules:
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 	* lock the filesystem
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-	* lock parents in "ancestors first" order.
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+	* lock parents in "ancestors first" order. If one is not ancestor of
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+	  the other, lock them in inode pointer order.
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 	* find source and target.
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 	* if old parent is equal to or is a descendent of target
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 	  fail with -ENOTEMPTY
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 	* if new parent is equal to or is a descendent of source
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 	  fail with -ELOOP
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-	* If it's an exchange, lock both the source and the target.
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-	* If the target exists, lock it.  If the source is a non-directory,
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-	  lock it.  If we need to lock both, do so in inode pointer order.
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+	* Lock both the source and the target provided they exist. If we
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+	  need to lock two inodes of different type (dir vs non-dir), we lock
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+	  the directory first. If we need to lock two inodes of the same type,
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+	  lock them in inode pointer order.
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 	* call the method.
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 All ->i_rwsem are taken exclusive.  Again, we might get away with locking
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@@ -66,8 +67,9 @@
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 Proof:
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-	First of all, at any moment we have a partial ordering of the
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-	objects - A < B iff A is an ancestor of B.
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+	First of all, at any moment we have a linear ordering of the
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+	objects - A < B iff (A is an ancestor of B) or (B is not an ancestor
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+        of A and ptr(A) < ptr(B)).
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 	That ordering can change.  However, the following is true:
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