Re: [PATCH 03/24] xfs: mark inode buffers in cache

Darrick J. Wong
2020-05-22T21:35:24Z

On Fri, May 22, 2020 at 01:50:08PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Inode buffers always have write IO callbacks, so by marking them
> directly we can avoid needing to attach ->b_iodone functions to
> them. This avoids an indirect call, and makes future modifications
> much simpler.
>
> This is largely a rearrangement of the code at this point - no IO
> completion functionality changes at this point, just how the
> code is run is modified.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_buf.c | 18 +++++++++++++-----
> fs/xfs/xfs_buf.h | 39 ++++++++++++++++++++++++++-------------
> fs/xfs/xfs_buf_item.c | 42 +++++++++++++++++++++++++++++++-----------
> fs/xfs/xfs_buf_item.h | 1 +
> fs/xfs/xfs_inode.c | 2 +-
> fs/xfs/xfs_trans_buf.c | 3 +++
> 6 files changed, 75 insertions(+), 30 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 9c2fbb6bbf89d..6105b97028d6a 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -14,6 +14,8 @@
> #include "xfs_mount.h"
> #include "xfs_trace.h"
> #include "xfs_log.h"
> +#include "xfs_trans.h"
> +#include "xfs_buf_item.h"
> #include "xfs_errortag.h"
> #include "xfs_error.h"
>
> @@ -1202,12 +1204,18 @@ xfs_buf_ioend(
> bp->b_flags |= XBF_DONE;
> }
>
> - if (bp->b_iodone)
> + /* inodes always have a callback on write */
> + if (!read && (bp->b_flags & _XBF_INODES)) {

I think this changes in the next patch.

> + xfs_buf_inode_iodone(bp);
> + return;
> + }
> +
> + if (bp->b_iodone) {
> (*(bp->b_iodone))(bp);
> - else if (bp->b_flags & XBF_ASYNC)
> - xfs_buf_relse(bp);
> - else
> - complete(&bp->b_iowait);
> + return;
> + }
> +
> + xfs_buf_ioend_finish(bp);
> }
>
> static void
> diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
> index 050c53b739e24..b3e5d653d09f1 100644
> --- a/fs/xfs/xfs_buf.h
> +++ b/fs/xfs/xfs_buf.h
> @@ -30,15 +30,19 @@
> #define XBF_STALE (1 << 6) /* buffer has been staled, do not find it */
> #define XBF_WRITE_FAIL (1 << 7) /* async writes have failed on this buffer */
>
> -/* flags used only as arguments to access routines */
> -#define XBF_TRYLOCK (1 << 16)/* lock requested, but do not wait */
> -#define XBF_UNMAPPED (1 << 17)/* do not map the buffer */
> +/* buffer type flags for write callbacks */
> +#define _XBF_INODES (1 << 16)/* inode buffer */
>
> /* flags used only internally */
> #define _XBF_PAGES (1 << 20)/* backed by refcounted pages */
> #define _XBF_KMEM (1 << 21)/* backed by heap memory */
> #define _XBF_DELWRI_Q (1 << 22)/* buffer on a delwri queue */
>
> +/* flags used only as arguments to access routines */
> +#define XBF_TRYLOCK (1 << 30)/* lock requested, but do not wait */
> +#define XBF_UNMAPPED (1 << 31)/* do not map the buffer */
> +
> +

Double newline?

> typedef unsigned int xfs_buf_flags_t;
>
> #define XFS_BUF_FLAGS \
> @@ -50,12 +54,13 @@ typedef unsigned int xfs_buf_flags_t;
> { XBF_DONE, "DONE" }, \
> { XBF_STALE, "STALE" }, \
> { XBF_WRITE_FAIL, "WRITE_FAIL" }, \
> - { XBF_TRYLOCK, "TRYLOCK" }, /* should never be set */\
> - { XBF_UNMAPPED, "UNMAPPED" }, /* ditto */\
> + { _XBF_INODES, "INODES" }, \

This a toughie. On the one hand if you're going to go introducing what
amounts to two-bit buffer io completion type in the middle of b_flags
then (like Amir says) this ideally would have a mask and switch
statements and whatnot.

I also wonder if we could tell the buffer type given all the
xfs_trans_buf_set_type calls, but I think the answer is that not every
buffer is guaranteed to have a buffer log item attached and a type code
set correctly?

OTOH there's only three states, so who cares, maybe this is fine...

--D

> { _XBF_PAGES, "PAGES" }, \
> { _XBF_KMEM, "KMEM" }, \
> - { _XBF_DELWRI_Q, "DELWRI_Q" }
> -
> + { _XBF_DELWRI_Q, "DELWRI_Q" }, \
> + /* The following interface flags should never be set */ \
> + { XBF_TRYLOCK, "TRYLOCK" }, \
> + { XBF_UNMAPPED, "UNMAPPED" }
>
> /*
> * Internal state flags.
> @@ -257,9 +262,23 @@ extern void xfs_buf_unlock(xfs_buf_t *);
> #define xfs_buf_islocked(bp) \
> ((bp)->b_sema.count <= 0)
>
> +static inline void xfs_buf_relse(xfs_buf_t *bp)
> +{
> + xfs_buf_unlock(bp);
> + xfs_buf_rele(bp);
> +}
> +
> /* Buffer Read and Write Routines */
> extern int xfs_bwrite(struct xfs_buf *bp);
> extern void xfs_buf_ioend(struct xfs_buf *bp);
> +static inline void xfs_buf_ioend_finish(struct xfs_buf *bp)
> +{
> + if (bp->b_flags & XBF_ASYNC)
> + xfs_buf_relse(bp);
> + else
> + complete(&bp->b_iowait);
> +}
> +
> extern void __xfs_buf_ioerror(struct xfs_buf *bp, int error,
> xfs_failaddr_t failaddr);
> #define xfs_buf_ioerror(bp, err) __xfs_buf_ioerror((bp), (err), __this_address)
> @@ -324,12 +343,6 @@ static inline int xfs_buf_ispinned(struct xfs_buf *bp)
> return atomic_read(&bp->b_pin_count);
> }
>
> -static inline void xfs_buf_relse(xfs_buf_t *bp)
> -{
> - xfs_buf_unlock(bp);
> - xfs_buf_rele(bp);
> -}
> -
> static inline int
> xfs_buf_verify_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
> {
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 9e75e8d6042ec..8659cf4282a64 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -1158,20 +1158,15 @@ xfs_buf_iodone_callback_error(
> return false;
> }
>
> -/*
> - * This is the iodone() function for buffers which have had callbacks attached
> - * to them by xfs_buf_attach_iodone(). We need to iterate the items on the
> - * callback list, mark the buffer as having no more callbacks and then push the
> - * buffer through IO completion processing.
> - */
> -void
> -xfs_buf_iodone_callbacks(
> +static void
> +xfs_buf_run_callbacks(
> struct xfs_buf *bp)
> {
> +
> /*
> - * If there is an error, process it. Some errors require us
> - * to run callbacks after failure processing is done so we
> - * detect that and take appropriate action.
> + * If there is an error, process it. Some errors require us to run
> + * callbacks after failure processing is done so we detect that and take
> + * appropriate action.
> */
> if (bp->b_error && xfs_buf_iodone_callback_error(bp))
> return;
> @@ -1188,9 +1183,34 @@ xfs_buf_iodone_callbacks(
> bp->b_log_item = NULL;
> list_del_init(&bp->b_li_list);
> bp->b_iodone = NULL;
> +}
> +
> +/*
> + * This is the iodone() function for buffers which have had callbacks attached
> + * to them by xfs_buf_attach_iodone(). We need to iterate the items on the
> + * callback list, mark the buffer as having no more callbacks and then push the
> + * buffer through IO completion processing.
> + */
> +void
> +xfs_buf_iodone_callbacks(
> + struct xfs_buf *bp)
> +{
> + xfs_buf_run_callbacks(bp);
> xfs_buf_ioend(bp);
> }
>
> +/*
> + * Inode buffer iodone callback function.
> + */
> +void
> +xfs_buf_inode_iodone(
> + struct xfs_buf *bp)
> +{
> + xfs_buf_run_callbacks(bp);
> + xfs_buf_ioend_finish(bp);
> +}
> +
> +
> /*
> * This is the iodone() function for buffers which have been
> * logged. It is called when they are eventually flushed out.
> diff --git a/fs/xfs/xfs_buf_item.h b/fs/xfs/xfs_buf_item.h
> index c9c57e2da9327..a342933ad9b8d 100644
> --- a/fs/xfs/xfs_buf_item.h
> +++ b/fs/xfs/xfs_buf_item.h
> @@ -59,6 +59,7 @@ void xfs_buf_attach_iodone(struct xfs_buf *,
> struct xfs_log_item *);
> void xfs_buf_iodone_callbacks(struct xfs_buf *);
> void xfs_buf_iodone(struct xfs_buf *, struct xfs_log_item *);
> +void xfs_buf_inode_iodone(struct xfs_buf *);
> bool xfs_buf_log_check_iovec(struct xfs_log_iovec *iovec);
>
> extern kmem_zone_t *xfs_buf_item_zone;
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 57781c0dbbec5..607c9d9bb2b40 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3841,13 +3841,13 @@ xfs_iflush_int(
> * completion on the buffer to remove the inode from the AIL and release
> * the flush lock.
> */
> + bp->b_flags |= _XBF_INODES;
> xfs_buf_attach_iodone(bp, xfs_iflush_done, &iip->ili_item);
>
> /* generate the checksum. */
> xfs_dinode_calc_crc(mp, dip);
>
> ASSERT(!list_empty(&bp->b_li_list));
> - ASSERT(bp->b_iodone != NULL);
> return error;
> }
>
> diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
> index 08174ffa21189..552d0869aa0fe 100644
> --- a/fs/xfs/xfs_trans_buf.c
> +++ b/fs/xfs/xfs_trans_buf.c
> @@ -626,6 +626,7 @@ xfs_trans_inode_buf(
> ASSERT(atomic_read(&bip->bli_refcount) > 0);
>
> bip->bli_flags |= XFS_BLI_INODE_BUF;
> + bp->b_flags |= _XBF_INODES;
> xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DINO_BUF);
> }
>
> @@ -651,6 +652,7 @@ xfs_trans_stale_inode_buf(
>
> bip->bli_flags |= XFS_BLI_STALE_INODE;
> bip->bli_item.li_cb = xfs_buf_iodone;
> + bp->b_flags |= _XBF_INODES;
> xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DINO_BUF);
> }
>
> @@ -675,6 +677,7 @@ xfs_trans_inode_alloc_buf(
> ASSERT(atomic_read(&bip->bli_refcount) > 0);
>
> bip->bli_flags |= XFS_BLI_INODE_ALLOC_BUF;
> + bp->b_flags |= _XBF_INODES;
> xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DINO_BUF);
> }
>
> --
> 2.26.2.761.g0e0b3e54be
>