Commit 4df3d265 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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ext4: Take read lock during overwrite case. 



When we are overwriting a file and not actually allocating new file system
blocks we need to take only the read lock on i_data_sem.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
parent 0e855ac8

fs/ext4/inode.c

+24 −8
Original line number Diff line number Diff line
@@ -901,11 +901,31 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block, 
			int create, int extend_disksize)

{

	int retval;

	if (create) {

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

	} else {

	/*

	 * Try to see if we can get  the block without requesting

	 * for new file system block.

	 */

	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, 0, 0);

	} else {

		retval = ext4_get_blocks_handle(handle,

				inode, block, max_blocks, bh, 0, 0);

	}

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

	if (!create || (retval > 0))

		return retval;



	/*

	 * We need to allocate new blocks which will result

	 * in i_data update

	 */

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

	/*

	 * We need to check for EXT4 here because migrate

	 * could have changed the inode type in between

	 */

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

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

				bh, create, extend_disksize);
@@ -913,11 +933,7 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block, 
		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;

}