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SubjectRe: [PATCH] support O_DIRECT in tmpfs/ramfs
Hua Zhong wrote:
> Hi,
> A while ago there was a discussion about supporting direct-io on tmpfs.
> Here is a simple patch that does it.
> 1. A new fs flag FS_RAM_BASED is added and the O_DIRECT flag is ignored
> if this flag is set (suggestions on a better name?)
> 2. Specify FS_RAM_BASED for tmpfs and ramfs.
> 3. When EINVAL is returned only a fput is done. I changed it to go
> through cleanup_all. But there is still a cleanup problem:
> If a new file is created and then EINVAL is returned due to O_DIRECT,
> the file is still left on the disk. I am not exactly sure how to fix
> it other than adding another fs flag so we could check O_DIRECT
> support at a much earlier stage. Comments on how to fix it?

This would seem to create two different sets of O_DIRECT semantics,
wouldn't it? I think that it would be possible to develop an application
using one of these FS_RAM_BASED file systems as the testbed, but then be
surprised when the application failed to work on other file systems such
as ext3.

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