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SubjectRe: [PATCH v2] fadvise: introduce POSIX_FADV_DONTNEED_FS
On Wed, Apr 27, 2011 at 08:13:47PM +0200, Andrea Righi wrote:
> @@ -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 (capable(CAP_SYS_ADMIN))
> + drop_pagecache_sb(file->f_dentry->d_sb, NULL);
> + else
> + ret = -EPERM;
> + break;
> default:
> ret = -EINVAL;
> }

Mmm ... what if I open /dev/sdxyz and call fadvise() on it? I think
you end up flushing /dev's page cache entries, instead of the filesystem
which is on /dev/sdxyz.

If I understand correctly, you want mapping->host->i_sb instead of
file->f_dentry->d_sb.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."


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