Maxim Patlasov <mpatla...@virtuozzo.com> writes:
> Before the patch, the only way to pick up updated file size from server (in a
> scenario when local inode was created earlier, then the file was updated
> from another node) was in fuse_open_common():
>
>> atomic_inc(&fi->num_openers);
>>
>> if (atomic_read(&fi->num_openers) == 1) {
>> err = fuse_getattr_size(inode, file, &size);
>> ...
>> spin_lock(&fc->lock);
>> i_size_write(inode, size);
>> spin_unlock(&fc->lock);
>> }
>
> This is correct, but someone may ask about i_size w/o open, e.g.: ls -l foo.
> The patch ensures that every time the server reports us some file size, if no
> open-s happened yet (num_openers=0), fuse stores that server size in local
> inode->i_size. This resolves the following problem:
>
> # pstorage-mount -c test -l /var/log/f1.log /pcs1
> # pstorage-mount -c test -l /var/log/f2.log /pcs2
>
> # date > /pcs1/foo; ls -l /pcs1/foo /pcs2/foo
> -rwx------ 1 root root 29 Dec 14 16:31 /pcs1/foo
> -rwx------ 1 root root 29 Dec 14 16:31 /pcs2/foo
>
> # date >> /pcs1/foo; ls -l /pcs1/foo /pcs2/foo
> -rwx------ 1 root root 58 Dec 14 16:31 /pcs1/foo
> -rwx------ 1 root root 29 Dec 14 16:31 /pcs2/foo
>
> https://jira.sw.ru/browse/PSBM-57047
>
> Signed-off-by: Maxim Patlasov <mpatla...@virtuozzo.com>
Ok. But IMHO fi->num_openers is redundant it protects special metadata,
but thre are other cases where we may get client/server mdata out of sync.
> ---
> fs/fuse/file.c | 12 +++++++++++-
> fs/fuse/fuse_i.h | 3 +++
> fs/fuse/inode.c | 4 +++-
> 3 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 9cad8c5..62967d2 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -296,12 +296,20 @@ int fuse_open_common(struct inode *inode, struct file
> *file, bool isdir)
> u64 size;
>
> mutex_lock(&inode->i_mutex);
> +
> + spin_lock(&fc->lock);
> atomic_inc(&fi->num_openers);
>
> if (atomic_read(&fi->num_openers) == 1) {
> + fi->i_size_unstable = 1;
> + spin_unlock(&fc->lock);
> err = fuse_getattr_size(inode, file, &size);
> if (err) {
> + spin_lock(&fc->lock);
> atomic_dec(&fi->num_openers);
> + fi->i_size_unstable = 0;
> + spin_unlock(&fc->lock);
> +
> mutex_unlock(&inode->i_mutex);
> fuse_release_common(file, FUSE_RELEASE);
> return err;
> @@ -309,8 +317,10 @@ int fuse_open_common(struct inode *inode, struct file
> *file, bool isdir)
>
> spin_lock(&fc->lock);
> i_size_write(inode, size);
> + fi->i_size_unstable = 0;
> + spin_unlock(&fc->lock);
> + } else
> spin_unlock(&fc->lock);
> - }
>
> mutex_unlock(&inode->i_mutex);
> }
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 1d24bf6..22eb9c9 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -124,6 +124,9 @@ struct fuse_inode {
>
> /** Mostly to detect very first open */
> atomic_t num_openers;
> +
> + /** Even though num_openers>0, trust server i_size */
> + int i_size_unstable;
> };
>
> /** FUSE inode state bits */
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 5ccecae..f606deb 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -97,6 +97,7 @@ static struct inode *fuse_alloc_inode(struct super_block
> *sb)
> fi->writectr = 0;
> fi->orig_ino = 0;
> fi->state = 0;
> + fi->i_size_unstable = 0;
> INIT_LIST_HEAD(&fi->write_files);
> INIT_LIST_HEAD(&fi->rw_files);
> INIT_LIST_HEAD(&fi->queued_writes);
> @@ -226,7 +227,8 @@ void fuse_change_attributes(struct inode *inode, struct
> fuse_attr *attr,
> * extend local i_size without keeping userspace server in sync. So,
> * attr->size coming from server can be stale. We cannot trust it.
> */
> - if (!is_wb || !S_ISREG(inode->i_mode))
> + if (!is_wb || !S_ISREG(inode->i_mode) ||
> + !atomic_read(&fi->num_openers) || fi->i_size_unstable)
> i_size_write(inode, attr->size);
> spin_unlock(&fc->lock);
>
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