Commit 4df3d265 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
Browse files

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
......@@ -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;
}
......
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