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SubjectRe: [PATCH] fadvise: introduce POSIX_FADV_DONTNEED_FS
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On Wednesday 27 April 2011 16:29:05 Andrea Righi wrote:
> diff --git a/include/linux/fadvise.h b/include/linux/fadvise.h
> index e8e7471..dc9ce98 100644
> --- a/include/linux/fadvise.h
> +++ b/include/linux/fadvise.h
> @@ -13,9 +13,11 @@
> #if defined(__s390x__)
> #define POSIX_FADV_DONTNEED 6 /* Don't need these pages. */
> #define POSIX_FADV_NOREUSE 7 /* Data will be accessed once. */
> +#define POSIX_FADV_DONTNEED_FS 8 /* Don't need these filesystem pages. */
> #else
> #define POSIX_FADV_DONTNEED 4 /* Don't need these pages. */
> #define POSIX_FADV_NOREUSE 5 /* Data will be accessed once. */
> +#define POSIX_FADV_DONTNEED_FS 6 /* Don't need these filesystem pages. */
> #endif
>
> #endif /* FADVISE_H_INCLUDED */

Please don't make the s390 mess worse than it already is here.
I think the best solution would be to assign new values starting
from 8 so they can be common for all architectures.

> @@ -127,6 +128,12 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
> invalidate_mapping_pages(mapping, start_index,
> end_index);
> break;
> + case POSIX_FADV_DONTNEED_FS:
> + if (!current_euid())
> + drop_pagecache_sb(file->f_dentry->d_sb, NULL);
> + else
> + ret = -EPERM;
> + break;

I somewhat disagree with keying the capability off the UID value, even
if that is what the sysctl uses. CAP_SYS_ADMIN is not that nice either, but
I think it's better than the UID here.

Aside from these, I like the patch.

Arnd


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