Re: [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK_{CUR,SET,END}

From: Christoph Hellwig
Date: Wed Nov 02 2011 - 04:29:24 EST


Andres, can you check with Chris that the btrfs changes made it to
his tree? The core lseek changes from Andi are in mainline now, but
I think these bits are better off going through Chrises btrfs tree.

On Sat, Oct 01, 2011 at 10:49:27PM +0200, Andres Freund wrote:
>
> Don't need the i_mutex for those cases, only for SEEK_HOLE/DATA.
>
> Really-From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Andres Freund <andres@xxxxxxxxxxx>
> ---
> fs/btrfs/file.c | 27 +++++++++++----------------
> 1 files changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 7a13337..5bc7116 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1809,24 +1809,19 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int origin)
> struct inode *inode = file->f_mapping->host;
> int ret;
>
> + if (origin != SEEK_DATA && origin != SEEK_HOLE)
> + return generic_file_llseek(file, offset, origin);
> +
> mutex_lock(&inode->i_mutex);
> - switch (origin) {
> - case SEEK_END:
> - case SEEK_CUR:
> - offset = generic_file_llseek(file, offset, origin);
> - goto out;
> - case SEEK_DATA:
> - case SEEK_HOLE:
> - if (offset >= i_size_read(inode)) {
> - mutex_unlock(&inode->i_mutex);
> - return -ENXIO;
> - }
> + if (offset >= i_size_read(inode)) {
> + mutex_unlock(&inode->i_mutex);
> + return -ENXIO;
> + }
>
> - ret = find_desired_extent(inode, &offset, origin);
> - if (ret) {
> - mutex_unlock(&inode->i_mutex);
> - return ret;
> - }
> + ret = find_desired_extent(inode, &offset, origin);
> + if (ret) {
> + mutex_unlock(&inode->i_mutex);
> + return ret;
> }
>
> if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
> --
> 1.7.6.409.ge7a85.dirty
>
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