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Date: Fri, 18 Dec 2009 15:24:44 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: Jiaying Zhang <jiayingz@...gle.com>
Cc: ext4 development <linux-ext4@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Michael Rubin <mrubin@...gle.com>
Subject: Re: [RFC PATCH 2/4] ext4: use ext4_get_block_write in buffer write
On Tue, Dec 15, 2009 at 05:39:08PM -0800, Jiaying Zhang wrote:
> ext4: use ext4_get_block_write in buffer write
>
> Allocate uninitialized extent before ext4 buffer write and
> convert the extent to initialized after io completes.
> The purpose is to make sure an extent can only be marked
> initialized after it has been written with new data so
> we can safely drop the i_mutex lock in ext4 DIO read without
> exposing stale data. This helps to improve multi-thread DIO
> read performance on high-speed disks.
>
> Skip the nobh and data=journal mount cases to make things simple for now.
>
> Signed-off-by: Jiaying Zhang <jiayingz@...gle.com>
> ---
> fs/ext4/ext4.h | 5 +++
> fs/ext4/extents.c | 10 +++---
> fs/ext4/fsync.c | 3 ++
> fs/ext4/inode.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++--------
> fs/ext4/super.c | 30 +++++++++++++++++---
> 5 files changed, 108 insertions(+), 21 deletions(-)
>
> Index: git-ext4/fs/ext4/extents.c
> ===================================================================
> --- git-ext4.orig/fs/ext4/extents.c 2009-12-15 16:03:05.000000000 -0800
> +++ git-ext4/fs/ext4/extents.c 2009-12-15 16:03:15.000000000 -0800
> @@ -3052,6 +3052,7 @@ ext4_ext_handle_uninitialized_extents(ha
> io->flag = EXT4_IO_UNWRITTEN;
> else
> EXT4_I(inode)->i_state |= EXT4_STATE_DIO_UNWRITTEN;
> + set_buffer_uninit(bh_result);
> goto out;
> }
> /* IO end_io complete, convert the filled extent to written */
> @@ -3291,11 +3292,9 @@ int ext4_ext_get_blocks(handle_t *handle
> if (flags & EXT4_GET_BLOCKS_UNINIT_EXT){
> ext4_ext_mark_uninitialized(&newex);
> /*
> - * io_end structure was created for every async
> - * direct IO write to the middle of the file.
> - * To avoid unecessary convertion for every aio dio rewrite
> - * to the mid of file, here we flag the IO that is really
> - * need the convertion.
> + * io_end structure was created for every IO write to an
> + * uninitialized extent. To avoid unecessary convertion,
> + * here we flag the IO that really needs the convertion.
> * For non asycn direct IO case, flag the inode state
> * that we need to perform convertion when IO is done.
> */
> @@ -3306,6 +3305,7 @@ int ext4_ext_get_blocks(handle_t *handle
> EXT4_I(inode)->i_state |=
> EXT4_STATE_DIO_UNWRITTEN;;
> }
> + set_buffer_uninit(bh_result);
> }
> err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
> if (err) {
> Index: git-ext4/fs/ext4/ext4.h
> ===================================================================
> --- git-ext4.orig/fs/ext4/ext4.h 2009-12-15 16:03:05.000000000 -0800
> +++ git-ext4/fs/ext4/ext4.h 2009-12-15 16:03:15.000000000 -0800
> @@ -134,6 +134,7 @@ struct mpage_da_data {
> int retval;
> };
> #define EXT4_IO_UNWRITTEN 0x1
> +#define EXT4_IO_WRITTEN 0x2
> typedef struct ext4_io_end {
> struct list_head list; /* per-file finished AIO list */
> struct inode *inode; /* file being written to */
> @@ -752,6 +753,7 @@ struct ext4_inode_info {
> #define EXT4_MOUNT_QUOTA 0x80000 /* Some quota option set */
> #define EXT4_MOUNT_USRQUOTA 0x100000 /* "old" user quota */
> #define EXT4_MOUNT_GRPQUOTA 0x200000 /* "old" group quota */
> +#define EXT4_MOUNT_DIOREAD_NOLOCK 0x400000 /* Enable support for
> dio read nolocking */
> #define EXT4_MOUNT_JOURNAL_CHECKSUM 0x800000 /* Journal checksums */
> #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal
> Async Commit */
> #define EXT4_MOUNT_I_VERSION 0x2000000 /* i_version support */
> @@ -1764,6 +1766,9 @@ static inline void set_bitmap_uptodate(s
> set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
> }
>
> +/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
> +#define BH_Uninit (BH_JBDPrivateStart + 1)
> +BUFFER_FNS(Uninit, uninit)
Why do we need to add a new buffer_head flag. Why is unwritten flag not sufficient
for this ?
> #endif /* __KERNEL__ */
>
> #endif /* _EXT4_H */
> Index: git-ext4/fs/ext4/super.c
> ===================================================================
> --- git-ext4.orig/fs/ext4/super.c 2009-12-15 16:03:05.000000000 -0800
> +++ git-ext4/fs/ext4/super.c 2009-12-15 16:03:15.000000000 -0800
> @@ -921,6 +921,9 @@ static int ext4_show_options(struct seq_
> if (test_opt(sb, NOLOAD))
> seq_puts(seq, ",norecovery");
>
> + if (test_opt(sb, DIOREAD_NOLOCK))
> + seq_puts(seq, ",dioread_nolock");
> +
> ext4_show_quota_options(seq, sb);
>
> return 0;
> @@ -1103,6 +1106,7 @@ enum {
> Opt_stripe, Opt_delalloc, Opt_nodelalloc,
> Opt_block_validity, Opt_noblock_validity,
> Opt_inode_readahead_blks, Opt_journal_ioprio,
> + Opt_dioread_nolock, Opt_dioread_lock,
> Opt_discard, Opt_nodiscard, Opt_akpm_lock_hack
> };
>
> @@ -1171,6 +1175,8 @@ static const match_table_t tokens = {
> {Opt_auto_da_alloc, "auto_da_alloc=%u"},
> {Opt_auto_da_alloc, "auto_da_alloc"},
> {Opt_noauto_da_alloc, "noauto_da_alloc"},
> + {Opt_dioread_nolock, "dioread_nolock"},
> + {Opt_dioread_lock, "dioread_lock"},
I guess this mount option will go away when we are ready to merge this
upstream ? If we want to merge i guess we should make this the default
behaviour.
Why version of the kernel are the patches against. I would like to take
a look at the changes after applying the patches.
-aneesh
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