Hi Ted,
On Sun, May 22, 2011 at 4:56 PM, Ted Ts'o <tytso@xxxxxxx> wrote:
> Here's a cleaner way of fixing the problem. vmtruncate() is now
> deprecated, so I'm using truncate_setsize() instead; in addition, I
> avoid calling ext4_truncate() twice in the case where EOFBLOCKS_FL.
> Since ext4_truncate() is a very heavyweight function, which requires
> manipulating the orphan list and taking i_data_sem, avoiding a double
> call of ext4_truncate() is a big win.
>
> - Ted
>
> commit bb5eabd2de1e9dfdeeac822174fba17f2d2a7f2b
> Author: Theodore Ts'o <tytso@xxxxxxx>
> Date: Sun May 22 19:45:01 2011 -0400
>
> ext4: use truncate_setsize() unconditionally
>
> In commit c8d46e41 (ext4: Add flag to files with blocks intentionally
> past EOF), if the EOFBLOCKS_FL flag is set, we call ext4_truncate()
> before calling vmtruncate(). This caused any allocated but unwritten
> blocks created by calling fallocate() with the FALLOC_FL_KEEP_SIZE
> flag to be dropped. This was done to make to make sure that
> EOFBLOCKS_FL would not be cleared while still leaving blocks past
> i_size allocated. This was not necessary, since ext4_truncate()
> guarantees that blocks past i_size will be dropped, even in the case
> where truncate() has increased i_size before calling ext4_truncate().
>
> So fix this by removing the EOFBLOCKS_FL special case treatment in
> ext4_setattr(). In addition, use truncate_setsize() followed by a
> call to ext4_truncate() instead of using vmtruncate(). This is more
> efficient since it skips the call to inode_newsize_ok(), which has
> been checked already by inode_change_ok(). This is also in a win in
> the case where EOFBLOCKS_FL is set since it avoids calling
> ext4_truncate() twice.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index df3fb20..4ca8411 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5363,8 +5363,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
>
> if (S_ISREG(inode->i_mode) &&
> attr->ia_valid & ATTR_SIZE &&
> - (attr->ia_size < inode->i_size ||
> - (ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)))) {
> + (attr->ia_size < inode->i_size)) {
> handle_t *handle;
>
> handle = ext4_journal_start(inode, 3);
> @@ -5398,14 +5397,13 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
> goto err_out;
> }
> }
> - /* ext4_truncate will clear the flag */
> - if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)))
> - ext4_truncate(inode);
> }
>
> if ((attr->ia_valid & ATTR_SIZE) &&
> - attr->ia_size != i_size_read(inode))
> - rc = vmtruncate(inode, attr->ia_size);
> + attr->ia_size != i_size_read(inode)) {
> + truncate_setsize(inode, attr->ia_size);
> + ext4_truncate(inode);
> + }
I think your patch doesn't cover the case when we fallocate with
KEEP_SIZE a 12k file, write 4k, and then truncate the file to 4k.
In this case, attr->ia_size is equal to i_size but we still want to
free any allocated but unwritten blocks during truncate.
Jiaying
>
> if (!rc) {
> setattr_copy(inode, attr);
>
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