From bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 24 Jun 2011 14:29:43 -0400 Subject: fs: kill i_alloc_sem i_alloc_sem is a rather special rw_semaphore. It's the last one that may be released by a non-owner, and it's write side is always mirrored by real exclusion. It's intended use it to wait for all pending direct I/O requests to finish before starting a truncate. Replace it with a hand-grown construct: - exclusion for truncates is already guaranteed by i_mutex, so it can simply fall way - the reader side is replaced by an i_dio_count member in struct inode that counts the number of pending direct I/O requests. Truncate can't proceed as long as it's non-zero - when i_dio_count reaches non-zero we wake up a pending truncate using wake_up_bit on a new bit in i_flags - new references to i_dio_count can't appear while we are waiting for it to read zero because the direct I/O count always needs i_mutex (or an equivalent like XFS's i_iolock) for starting a new operation. This scheme is much simpler, and saves the space of a spinlock_t and a struct list_head in struct inode (typically 160 bits on a non-debug 64-bit system). Signed-off-by: Christoph Hellwig Signed-off-by: Al Viro --- include/linux/fs.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 1393742bba9..2fe920774ab 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -779,7 +779,7 @@ struct inode { struct timespec i_ctime; blkcnt_t i_blocks; unsigned short i_bytes; - struct rw_semaphore i_alloc_sem; + atomic_t i_dio_count; const struct file_operations *i_fop; /* former ->i_op->default_file_ops */ struct file_lock *i_flock; struct address_space *i_mapping; @@ -1705,6 +1705,10 @@ struct super_operations { * set during data writeback, and cleared with a wakeup * on the bit address once it is done. * + * I_REFERENCED Marks the inode as recently references on the LRU list. + * + * I_DIO_WAKEUP Never set. Only used as a key for wait_on_bit(). + * * Q: What is the difference between I_WILL_FREE and I_FREEING? */ #define I_DIRTY_SYNC (1 << 0) @@ -1718,6 +1722,8 @@ struct super_operations { #define __I_SYNC 7 #define I_SYNC (1 << __I_SYNC) #define I_REFERENCED (1 << 8) +#define __I_DIO_WAKEUP 9 +#define I_DIO_WAKEUP (1 << I_DIO_WAKEUP) #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES) @@ -1828,7 +1834,6 @@ struct file_system_type { struct lock_class_key i_lock_key; struct lock_class_key i_mutex_key; struct lock_class_key i_mutex_dir_key; - struct lock_class_key i_alloc_sem_key; }; extern struct dentry *mount_ns(struct file_system_type *fs_type, int flags, @@ -2404,6 +2409,8 @@ enum { }; void dio_end_io(struct bio *bio, int error); +void inode_dio_wait(struct inode *inode); +void inode_dio_done(struct inode *inode); ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, struct block_device *bdev, const struct iovec *iov, loff_t offset, -- cgit v1.2.3-70-g09d2