On Sep 25, 2009 17:31 +0900, Akira Fujita wrote:
> ext4: Add checks whether two inodes are different to move_extent.c
>
> From: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
>
> If same inode is set to orig and donor in ext4_move_extensts(),
> this leads to the deadlock in mext_double_down_{read, write}.
> This patch adds checks to mext_double_{down, up}_{read, write}
> and if inodes are same, we take/release one semaphore from them.
Wouldn't it make more sense to just return an error (or no error
but do nothing) in the case of source/target inode being the same?
I don't see how that would be good to "defragment" the inode onto
itself, just like "cp f f" and "rename f f" don't make sense either.
> Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
> ---
> fs/ext4/move_extent.c | 14 +++++++++-----
> 1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index c07a291..e1346cb 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -177,7 +177,8 @@ mext_double_down_read(struct inode *orig_inode, struct inode *donor_inode)
> }
>
> down_read(&EXT4_I(first)->i_data_sem);
> - down_read(&EXT4_I(second)->i_data_sem);
> + if (first != second)
> + down_read(&EXT4_I(second)->i_data_sem);
> }
>
> /**
> @@ -203,7 +204,8 @@ mext_double_down_write(struct inode *orig_inode, struct inode *donor_inode)
> }
>
> down_write(&EXT4_I(first)->i_data_sem);
> - down_write(&EXT4_I(second)->i_data_sem);
> + if (first != second)
> + down_write(&EXT4_I(second)->i_data_sem);
> }
>
> /**
> @@ -217,7 +219,8 @@ static void
> mext_double_up_read(struct inode *orig_inode, struct inode *donor_inode)
> {
> up_read(&EXT4_I(orig_inode)->i_data_sem);
> - up_read(&EXT4_I(donor_inode)->i_data_sem);
> + if (orig_inode != donor_inode)
> + up_read(&EXT4_I(donor_inode)->i_data_sem);
> }
>
> /**
> @@ -231,7 +234,8 @@ static void
> mext_double_up_write(struct inode *orig_inode, struct inode *donor_inode)
> {
> up_write(&EXT4_I(orig_inode)->i_data_sem);
> - up_write(&EXT4_I(donor_inode)->i_data_sem);
> + if (orig_inode != donor_inode)
> + up_write(&EXT4_I(donor_inode)->i_data_sem);
> }
>
> /**
> @@ -1002,7 +1006,7 @@ mext_check_arguments(struct inode *orig_inode,
> }
>
> /* orig and donor should be different file */
> - if (orig_inode->i_ino == donor_inode->i_ino) {
> + if (orig_inode == donor_inode) {
> ext4_debug("ext4 move extent: The argument files should not "
> "be same file [ino:orig %lu, donor %lu]\n",
> orig_inode->i_ino, donor_inode->i_ino);
>
> --
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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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