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ext4: factor out checks from ext4_file_write_iter() 

Factor out checks of 'from' and whether we are overwriting out of
ext4_file_write_iter() so that the function is easier to follow.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2016-11-20 17:29:51 -05:00 committed by Theodore Ts'o
parent c48ae41baf
commit 213bcd9ccb
1 changed files with 50 additions and 47 deletions
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97
fs/ext4/file.c
View File

@ -88,6 +88,51 @@ ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
return 0;
}
/* Is IO overwriting allocated and initialized blocks? */
static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
{
struct ext4_map_blocks map;
unsigned int blkbits = inode->i_blkbits;
int err, blklen;
if (pos + len > i_size_read(inode))
return false;
map.m_lblk = pos >> blkbits;
map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
blklen = map.m_len;
err = ext4_map_blocks(NULL, inode, &map, 0);
/*
* 'err==len' means that all of the blocks have been preallocated,
* regardless of whether they have been initialized or not. To exclude
* unwritten extents, we need to check m_flags.
*/
return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
}
static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
ssize_t ret;
ret = generic_write_checks(iocb, from);
if (ret <= 0)
return ret;
/*
* If we have encountered a bitmap-format file, the size limit
* is smaller than s_maxbytes, which is for extent-mapped files.
*/
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
return -EFBIG;
iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
}
return iov_iter_count(from);
}
static ssize_t
ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
@ -98,7 +143,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
ssize_t ret;
inode_lock(inode);
ret = generic_write_checks(iocb, from);
ret = ext4_write_checks(iocb, from);
if (ret <= 0)
goto out;
@ -114,53 +159,11 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
ext4_unwritten_wait(inode);
}
/*
* If we have encountered a bitmap-format file, the size limit
* is smaller than s_maxbytes, which is for extent-mapped files.
*/
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
if (iocb->ki_pos >= sbi->s_bitmap_maxbytes) {
ret = -EFBIG;
goto out;
}
iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
}
iocb->private = &overwrite;
if (o_direct) {
size_t length = iov_iter_count(from);
loff_t pos = iocb->ki_pos;
/* check whether we do a DIO overwrite or not */
if (ext4_should_dioread_nolock(inode) && !unaligned_aio &&
pos + length <= i_size_read(inode)) {
struct ext4_map_blocks map;
unsigned int blkbits = inode->i_blkbits;
int err, len;
map.m_lblk = pos >> blkbits;
map.m_len = EXT4_MAX_BLOCKS(length, pos, blkbits);
len = map.m_len;
err = ext4_map_blocks(NULL, inode, &map, 0);
/*
* 'err==len' means that all of blocks has
* been preallocated no matter they are
* initialized or not. For excluding
* unwritten extents, we need to check
* m_flags. There are two conditions that
* indicate for initialized extents. 1) If we
* hit extent cache, EXT4_MAP_MAPPED flag is
* returned; 2) If we do a real lookup,
* non-flags are returned. So we should check
* these two conditions.
*/
if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
overwrite = 1;
}
}
/* Check whether we do a DIO overwrite or not */
if (o_direct && ext4_should_dioread_nolock(inode) && !unaligned_aio &&
ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from)))
overwrite = 1;
ret = __generic_file_write_iter(iocb, from);
inode_unlock(inode);