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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: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
Aneesh Kumar K.V 2008-01-28 23:58:29 -05:00 committed by Theodore Ts'o
parent 0e855ac8b1
commit 4df3d265bf
1 changed files with 24 additions and 8 deletions
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32
fs/ext4/inode.c
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@ -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));
/*
* 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 {
down_read((&EXT4_I(inode)->i_data_sem));
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));
}
up_write((&EXT4_I(inode)->i_data_sem));
return retval;
}