On Sat, Feb 25, 2012 at 10:27 AM, Eric Wong <normalperson@xxxxxxxx> wrote:
> The kernel is not required to act on fadvise, so fail silently
> and ignore advice as long as it has a valid descriptor and
> parameters.
>
> Cc: linux-mm@xxxxxxxxx
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Eric Wong <normalperson@xxxxxxxx>
> ---
>
> Of course I wouldn't knowingly call posix_fadvise() on a file in
> tmpfs, but a userspace app often doesn't know (nor should it
> care) what type of filesystem it's on.
>
> I encountered EINVAL while running the Ruby 1.9.3 test suite on a
> stock Debian wheezy installation. Wheezy uses tmpfs for "/tmp" by
> default and the test suite creates a temporary file to test the
> Ruby wrapper for posix_fadvise() on.
>
> mm/fadvise.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/mm/fadvise.c b/mm/fadvise.c
> index 469491e0..f9e48dd 100644
> --- a/mm/fadvise.c
> +++ b/mm/fadvise.c
> @@ -43,13 +43,13 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
> goto out;
> }
>
> - mapping = file->f_mapping;
> - if (!mapping || len < 0) {
> + if (len < 0) {
Current code makes sure mapping is valid after the above check,
> ret = -EINVAL;
> goto out;
> }
>
> - if (mapping->a_ops->get_xip_mem) {
> + mapping = file->f_mapping;
> + if (!mapping || mapping->a_ops->get_xip_mem) {
> switch (advice) {
> case POSIX_FADV_NORMAL:
> case POSIX_FADV_RANDOM:
but backing devices info is no longer evaluated with that
guarantee in your change.
-hd
75: bdi = mapping->backing_dev_info;
> @@ -93,10 +93,9 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
> spin_unlock(&file->f_lock);
> break;
> case POSIX_FADV_WILLNEED:
> - if (!mapping->a_ops->readpage) {
> - ret = -EINVAL;
> + /* ignore the advice if readahead isn't possible (tmpfs) */
> + if (!mapping->a_ops->readpage)
> break;
> - }
>
> /* First and last PARTIAL page! */
> start_index = offset >> PAGE_CACHE_SHIFT;
> @@ -106,12 +105,8 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
> nrpages = end_index - start_index + 1;
> if (!nrpages)
> nrpages = ~0UL;
> -
> - ret = force_page_cache_readahead(mapping, file,
> - start_index,
> - nrpages);
> - if (ret > 0)
> - ret = 0;
> +
> + force_page_cache_readahead(mapping, file, start_index, nrpages);
> break;
> case POSIX_FADV_NOREUSE:
> break;
> --
> Eric Wong
> --
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>
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