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    SubjectRe: [PATCH v2] fadvise: introduce POSIX_FADV_DONTNEED_FS
    On Wed, Apr 27, 2011 at 14:33, Matthew Wilcox wrote:
    > 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.

    i was thinking of that, but was trying to come up with situations
    where there might not have a node to work on. fs's in a file go
    through loop devs, dm/lvm have ones created, and flash fs's still have
    a mtd block. how about network based fs's ? how you going to signal
    dropping of pages for nfs or cifs or fuse ones ?
    -mike
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