svn commit: r221166 - in head/sys: fs/ext2fs modules/ext2fs

[Kostik Belousov]

On Thu, Apr 28, 2011 at 02:27:17PM +0000, John Baldwin wrote:
> Author: jhb
> Date: Thu Apr 28 14:27:17 2011
> New Revision: 221166
> URL: http://svn.freebsd.org/changeset/base/221166
> 
> Log:
>   Sync with several changes in UFS/FFS:
>   - 77115: Implement support for O_DIRECT.
>   - 98425: Fix a performance issue introduced in 70131 that was causing
>     reads before writes even when writing full blocks.
>   - 98658: Rename the BALLOC flags from B_* to BA_* to avoid confusion with
>     the struct buf B_ flags.
>   - 100344: Merge the BA_ and IO_ flags so so that they may both be used in
>     the same flags word. This merger is possible by assigning the IO_ flags
>     to the low sixteen bits and the BA_ flags the high sixteen bits.
>   - 105422: Fix a file-rewrite performance case.
>   - 129545: Implement IO_INVAL in VOP_WRITE() by marking the buffer as
>     "no cache".
>   - Readd the DOINGASYNC() macro and use it to control asynchronous writes.
>     Change i-node updates to honor DOINGASYNC() instead of always being
>     synchronous.
>   - Use a PRIV_VFS_RETAINSUGID check instead of checking cr_uid against 0
>     directly when deciding whether or not to clear suid and sgid bits.
>   
>   Submitted by:	Pedro F. Giffuni  giffunip at yahoo
> 

> @@ -141,10 +162,42 @@ READ(ap)
>  		if (error)
>  			break;
>  
> -		bqrelse(bp);
> +		if ((ioflag & (IO_VMIO|IO_DIRECT)) &&
> +		   (LIST_FIRST(&bp->b_dep) == NULL)) {
> +			/*
> +			 * If there are no dependencies, and it's VMIO,
There is no dependencies for ext2fs, the FFS comments talks about SU.

Also, I am unsure what the resulting semantic of O_DIRECTIO for ext2
is ? UFS tries to eliminate any use of buffer cache for O_DIRECTIO
case, up to the mapping of user pages into pbuf to perform the
actual i/o. In ext2 case, it seems we will just destroy the buffers
after using them for i/o. Is it useful ?

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