fs/ceph/io: make ceph_start_io_*() killable

This allows killing processes that wait for a lock when one process is
stuck waiting for the Ceph server.  This is similar to the NFS commit
38a125b31504 ("fs/nfs/io: make nfs_start_io_*() killable").

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 fs/ceph/file.c | 22 +++++++++++++---------
 fs/ceph/io.c   | 44 +++++++++++++++++++++++++++++++++-----------
 fs/ceph/io.h   |  8 +++++---
 3 files changed, 51 insertions(+), 23 deletions(-)

What happened to this patch submission? Similar patches were accepted
in NFS and VFS core.

On Fri, Dec 6, 2024 at 5:50 PM Max Kellermann <max.kellermann@ionos.com> wrote:
>
> This allows killing processes that wait for a lock when one process is
> stuck waiting for the Ceph server.  This is similar to the NFS commit
> 38a125b31504 ("fs/nfs/io: make nfs_start_io_*() killable").
>
> Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
> ---
>  fs/ceph/file.c | 22 +++++++++++++---------
>  fs/ceph/io.c   | 44 +++++++++++++++++++++++++++++++++-----------
>  fs/ceph/io.h   |  8 +++++---
>  3 files changed, 51 insertions(+), 23 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 4b8d59ebda00..d79c0774dc6e 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -2127,10 +2127,11 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
>         if (ceph_inode_is_shutdown(inode))
>                 return -ESTALE;
>
> -       if (direct_lock)
> -               ceph_start_io_direct(inode);
> -       else
> -               ceph_start_io_read(inode);
> +       ret = direct_lock
> +               ? ceph_start_io_direct(inode)
> +               : ceph_start_io_read(inode);
> +       if (ret)
> +               return ret;
>
>         if (!(fi->flags & CEPH_F_SYNC) && !direct_lock)
>                 want |= CEPH_CAP_FILE_CACHE;
> @@ -2283,7 +2284,9 @@ static ssize_t ceph_splice_read(struct file *in, loff_t *ppos,
>             (fi->flags & CEPH_F_SYNC))
>                 return copy_splice_read(in, ppos, pipe, len, flags);
>
> -       ceph_start_io_read(inode);
> +       ret = ceph_start_io_read(inode);
> +       if (ret)
> +               return ret;
>
>         want = CEPH_CAP_FILE_CACHE;
>         if (fi->fmode & CEPH_FILE_MODE_LAZY)
> @@ -2362,10 +2365,11 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
>                 direct_lock = true;
>
>  retry_snap:
> -       if (direct_lock)
> -               ceph_start_io_direct(inode);
> -       else
> -               ceph_start_io_write(inode);
> +       err = direct_lock
> +               ? ceph_start_io_direct(inode)
> +               : ceph_start_io_write(inode);
> +       if (err)
> +               goto out_unlocked;
>
>         if (iocb->ki_flags & IOCB_APPEND) {
>                 err = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
> diff --git a/fs/ceph/io.c b/fs/ceph/io.c
> index c456509b31c3..2735503bc479 100644
> --- a/fs/ceph/io.c
> +++ b/fs/ceph/io.c
> @@ -47,20 +47,30 @@ static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode)
>   * Note that buffered writes and truncates both take a write lock on
>   * inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
>   */
> -void
> +int
>  ceph_start_io_read(struct inode *inode)
>  {
>         struct ceph_inode_info *ci = ceph_inode(inode);
> +       int err;
>
>         /* Be an optimist! */
> -       down_read(&inode->i_rwsem);
> +       err = down_read_killable(&inode->i_rwsem);
> +       if (err)
> +               return err;
> +
>         if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT))
> -               return;
> +               return 0;
>         up_read(&inode->i_rwsem);
> +
>         /* Slow path.... */
> -       down_write(&inode->i_rwsem);
> +       err = down_write_killable(&inode->i_rwsem);
> +       if (err)
> +               return err;
> +
>         ceph_block_o_direct(ci, inode);
>         downgrade_write(&inode->i_rwsem);
> +
> +       return 0;
>  }
>
>  /**
> @@ -83,11 +93,13 @@ ceph_end_io_read(struct inode *inode)
>   * Declare that a buffered write operation is about to start, and ensure
>   * that we block all direct I/O.
>   */
> -void
> +int
>  ceph_start_io_write(struct inode *inode)
>  {
> -       down_write(&inode->i_rwsem);
> -       ceph_block_o_direct(ceph_inode(inode), inode);
> +       int err = down_write_killable(&inode->i_rwsem);
> +       if (!err)
> +               ceph_block_o_direct(ceph_inode(inode), inode);
> +       return err;
>  }
>
>  /**
> @@ -133,20 +145,30 @@ static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode)
>   * Note that buffered writes and truncates both take a write lock on
>   * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
>   */
> -void
> +int
>  ceph_start_io_direct(struct inode *inode)
>  {
>         struct ceph_inode_info *ci = ceph_inode(inode);
> +       int err;
>
>         /* Be an optimist! */
> -       down_read(&inode->i_rwsem);
> +       err = down_read_killable(&inode->i_rwsem);
> +       if (err)
> +               return err;
> +
>         if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)
> -               return;
> +               return 0;
>         up_read(&inode->i_rwsem);
> +
>         /* Slow path.... */
> -       down_write(&inode->i_rwsem);
> +       err = down_write_killable(&inode->i_rwsem);
> +       if (err)
> +               return err;
> +
>         ceph_block_buffered(ci, inode);
>         downgrade_write(&inode->i_rwsem);
> +
> +       return 0;
>  }
>
>  /**
> diff --git a/fs/ceph/io.h b/fs/ceph/io.h
> index fa594cd77348..08d58253f533 100644
> --- a/fs/ceph/io.h
> +++ b/fs/ceph/io.h
> @@ -2,11 +2,13 @@
>  #ifndef _FS_CEPH_IO_H
>  #define _FS_CEPH_IO_H
>
> -void ceph_start_io_read(struct inode *inode);
> +#include <linux/compiler_attributes.h> // for __must_check
> +
> +__must_check int ceph_start_io_read(struct inode *inode);
>  void ceph_end_io_read(struct inode *inode);
> -void ceph_start_io_write(struct inode *inode);
> +__must_check int ceph_start_io_write(struct inode *inode);
>  void ceph_end_io_write(struct inode *inode);
> -void ceph_start_io_direct(struct inode *inode);
> +__must_check int ceph_start_io_direct(struct inode *inode);
>  void ceph_end_io_direct(struct inode *inode);
>
>  #endif /* FS_CEPH_IO_H */
> --
> 2.45.2
>