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Commit 0e855ac8 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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ext4: Convert truncate_mutex to read write semaphore. 



We are currently taking the truncate_mutex for every read. This would have
performance impact on large CPU configuration. Convert the lock to read write
semaphore and take read lock when we are trying to read the file.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
parent c278bfec

fs/ext4/balloc.c

+1 −1
Original line number Diff line number Diff line
@@ -526,7 +526,7 @@ static inline int rsv_is_empty(struct ext4_reserve_window *rsv) 
 * when setting the reservation window size through ioctl before the file

 * is open for write (needs block allocation).

 *

 * Needs truncate_mutex protection prior to call this function.

 * Needs down_write(i_data_sem) protection prior to call this function.

 */

void ext4_init_block_alloc_info(struct inode *inode)

{

fs/ext4/extents.c

+7 −6
Original line number Diff line number Diff line
@@ -1565,7 +1565,7 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode, 
 * This routine returns max. credits that the extent tree can consume.

 * It should be OK for low-performance paths like ->writepage()

 * To allow many writing processes to fit into a single transaction,

 * the caller should calculate credits under truncate_mutex and

 * the caller should calculate credits under i_data_sem and

 * pass the actual path.

 */

int ext4_ext_calc_credits_for_insert(struct inode *inode,
@@ -2131,7 +2131,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, 


/*

 * Need to be called with

 * mutex_lock(&EXT4_I(inode)->truncate_mutex);

 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block

 * (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem)

 */

int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,

			ext4_lblk_t iblock,
@@ -2350,7 +2351,7 @@ void ext4_ext_truncate(struct inode * inode, struct page *page) 
	if (page)

		ext4_block_truncate_page(handle, page, mapping, inode->i_size);



	mutex_lock(&EXT4_I(inode)->truncate_mutex);

	down_write(&EXT4_I(inode)->i_data_sem);

	ext4_ext_invalidate_cache(inode);



	/*
@@ -2386,7 +2387,7 @@ void ext4_ext_truncate(struct inode * inode, struct page *page) 
	if (inode->i_nlink)

		ext4_orphan_del(handle, inode);



	mutex_unlock(&EXT4_I(inode)->truncate_mutex);

	up_write(&EXT4_I(inode)->i_data_sem);

	ext4_journal_stop(handle);

}
@@ -2450,7 +2451,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
	 * modify 1 super block, 1 block bitmap and 1 group descriptor.

	 */

	credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;

	mutex_lock(&EXT4_I(inode)->truncate_mutex)

	down_write((&EXT4_I(inode)->i_data_sem));

retry:

	while (ret >= 0 && ret < max_blocks) {

		block = block + ret;
@@ -2507,7 +2508,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))

		goto retry;



	mutex_unlock(&EXT4_I(inode)->truncate_mutex)

	up_write((&EXT4_I(inode)->i_data_sem));

	/*

	 * Time to update the file size.

	 * Update only when preallocation was requested beyond the file size.

fs/ext4/file.c

+2 −2
Original line number Diff line number Diff line
@@ -37,9 +37,9 @@ static int ext4_release_file (struct inode * inode, struct file * filp) 
	if ((filp->f_mode & FMODE_WRITE) &&

			(atomic_read(&inode->i_writecount) == 1))

	{

		mutex_lock(&EXT4_I(inode)->truncate_mutex);

		down_write(&EXT4_I(inode)->i_data_sem);

		ext4_discard_reservation(inode);

		mutex_unlock(&EXT4_I(inode)->truncate_mutex);

		up_write(&EXT4_I(inode)->i_data_sem);

	}

	if (is_dx(inode) && filp->private_data)

		ext4_htree_free_dir_info(filp->private_data);

fs/ext4/inode.c

+33 −7
Original line number Diff line number Diff line
@@ -308,7 +308,7 @@ static int ext4_block_to_path(struct inode *inode, 
		final = ptrs;

	} else {

		ext4_warning(inode->i_sb, "ext4_block_to_path",

				"block %u > max",

				"block %lu > max",

				i_block + direct_blocks +

				indirect_blocks + double_blocks);

	}
@@ -345,7 +345,7 @@ static int ext4_block_to_path(struct inode *inode, 
 *	the whole chain, all way to the data (returns %NULL, *err == 0).

 *

 *      Need to be called with

 *      mutex_lock(&EXT4_I(inode)->truncate_mutex)

 *      down_read(&EXT4_I(inode)->i_data_sem)

 */

static Indirect *ext4_get_branch(struct inode *inode, int depth,

				 ext4_lblk_t  *offsets,
@@ -777,7 +777,8 @@ static int ext4_splice_branch(handle_t *handle, struct inode *inode, 
 *

 *

 * Need to be called with

 * mutex_lock(&EXT4_I(inode)->truncate_mutex)

 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block

 * (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem)

 */

int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,

		ext4_lblk_t iblock, unsigned long maxblocks,
@@ -865,7 +866,7 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode, 
		err = ext4_splice_branch(handle, inode, iblock,

					partial, indirect_blks, count);

	/*

	 * i_disksize growing is protected by truncate_mutex.  Don't forget to

	 * i_disksize growing is protected by i_data_sem.  Don't forget to

	 * protect it if you're about to implement concurrent

	 * ext4_get_block() -bzzz

	*/
@@ -895,6 +896,31 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode, 


#define DIO_CREDITS (EXT4_RESERVE_TRANS_BLOCKS + 32)



int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,

			unsigned long max_blocks, struct buffer_head *bh,

			int create, int extend_disksize)

{

	int retval;

	if (create) {

		down_write((&EXT4_I(inode)->i_data_sem));

	} else {

		down_read((&EXT4_I(inode)->i_data_sem));

	}

	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {

		retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,

				bh, create, extend_disksize);

	} else {

		retval = ext4_get_blocks_handle(handle, inode, block,

				max_blocks, bh, create, extend_disksize);

	}

	if (create) {

		up_write((&EXT4_I(inode)->i_data_sem));

	} else {

		up_read((&EXT4_I(inode)->i_data_sem));

	}

	return retval;

}



static int ext4_get_block(struct inode *inode, sector_t iblock,

			struct buffer_head *bh_result, int create)

{
@@ -1399,7 +1425,7 @@ static int jbd2_journal_dirty_data_fn(handle_t *handle, struct buffer_head *bh) 
 *	ext4_file_write() -> generic_file_write() -> __alloc_pages() -> ...

 *

 * Same applies to ext4_get_block().  We will deadlock on various things like

 * lock_journal and i_truncate_mutex.

 * lock_journal and i_data_sem

 *

 * Setting PF_MEMALLOC here doesn't work - too many internal memory

 * allocations fail.
@@ -2325,7 +2351,7 @@ void ext4_truncate(struct inode *inode) 
	 * From here we block out all ext4_get_block() callers who want to

	 * modify the block allocation tree.

	 */

	mutex_lock(&ei->truncate_mutex);

	down_write(&ei->i_data_sem);



	if (n == 1) {		/* direct blocks */

		ext4_free_data(handle, inode, NULL, i_data+offsets[0],
@@ -2389,7 +2415,7 @@ void ext4_truncate(struct inode *inode) 


	ext4_discard_reservation(inode);



	mutex_unlock(&ei->truncate_mutex);

	up_write(&ei->i_data_sem);

	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);

	ext4_mark_inode_dirty(handle, inode);

fs/ext4/ioctl.c

+2 −2
Original line number Diff line number Diff line
@@ -199,7 +199,7 @@ int ext4_ioctl (struct inode * inode, struct file * filp, unsigned int cmd, 
		 * need to allocate reservation structure for this inode

		 * before set the window size

		 */

		mutex_lock(&ei->truncate_mutex);

		down_write(&ei->i_data_sem);

		if (!ei->i_block_alloc_info)

			ext4_init_block_alloc_info(inode);
@@ -207,7 +207,7 @@ int ext4_ioctl (struct inode * inode, struct file * filp, unsigned int cmd, 
			struct ext4_reserve_window_node *rsv = &ei->i_block_alloc_info->rsv_window_node;

			rsv->rsv_goal_size = rsv_window_size;

		}

		mutex_unlock(&ei->truncate_mutex);

		up_write(&ei->i_data_sem);

		return 0;

	}

	case EXT4_IOC_GROUP_EXTEND: {