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[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>
hifive-unleashed-5.1
Miklos Szeredi 2006-10-17 00:10:07 -07:00 committed by Linus Torvalds
parent 9ffbb91623
commit 7762f5a0b7
1 changed files with 5 additions and 1 deletions
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6
include/linux/fs.h
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@ -656,7 +656,11 @@ static inline loff_t i_size_read(struct inode *inode)
#endif
}
/*
* NOTE: unlike i_size_read(), i_size_write() does need locking around it
* (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
* can be lost, resulting in subsequent i_size_read() calls spinning forever.
*/
static inline void i_size_write(struct inode *inode, loff_t i_size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)