[PATCH] document i_size_write locking rules
Unless someone reads the documentation for write_seqcount_{begin,end} it is not obvious, that i_size_write() needs locking. Especially, that lack of such locking can result in a system hang. Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -656,7 +656,11 @@ static inline loff_t i_size_read(struct inode *inode)
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#endif
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}
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/*
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* NOTE: unlike i_size_read(), i_size_write() does need locking around it
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* (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
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* can be lost, resulting in subsequent i_size_read() calls spinning forever.
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*/
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static inline void i_size_write(struct inode *inode, loff_t i_size)
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{
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#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
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