linux/fs/fscache
David Howells 102f4d900c FS-Cache: Handle a write to the page immediately beyond the EOF marker
Handle a write being requested to the page immediately beyond the EOF
marker on a cache object.  Currently this gets an assertion failure in
CacheFiles because the EOF marker is used there to encode information about
a partial page at the EOF - which could lead to an unknown blank spot in
the file if we extend the file over it.

The problem is actually in fscache where we check the index of the page
being written against store_limit.  store_limit is set to the number of
pages that we're allowed to store by fscache_set_store_limit() - which
means it's one more than the index of the last page we're allowed to store.
The problem is that we permit writing to a page with an index _equal_ to
the store limit - when we should reject that case.

Whilst we're at it, change the triggered assertion in CacheFiles to just
return -ENOBUFS instead.

The assertion failure looks something like this:

CacheFiles: Assertion failed
1000 < 7b1 is false
------------[ cut here ]------------
kernel BUG at fs/cachefiles/rdwr.c:962!
...
RIP: 0010:[<ffffffffa02c9e83>]  [<ffffffffa02c9e83>] cachefiles_write_page+0x273/0x2d0 [cachefiles]

Cc: stable@vger.kernel.org # v2.6.31+; earlier - that + backport of a17754f (at least)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-11-11 02:11:02 -05:00
..
cache.c fs/fscache: convert printk to pr_foo() 2014-06-04 16:53:51 -07:00
cookie.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
fsdef.c FS-Cache: Provide the ability to enable/disable cookies 2013-09-27 18:40:25 +01:00
histogram.c fs/fscache: replace seq_printf by seq_puts 2014-06-04 16:53:52 -07:00
internal.h FS-Cache: The operation cancellation method needs calling in more places 2015-04-02 14:28:53 +01:00
Kconfig
main.c fs/fscache: make ctl_table static 2014-08-06 18:01:12 -07:00
Makefile
netfs.c FS-Cache: Don't override netfs's primary_index if registering failed 2015-11-11 02:07:51 -05:00
object-list.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
object.c FS-Cache: The operation cancellation method needs calling in more places 2015-04-02 14:28:53 +01:00
operation.c FS-Cache: Retain the netfs context in the retrieval op earlier 2015-04-02 14:28:53 +01:00
page.c FS-Cache: Handle a write to the page immediately beyond the EOF marker 2015-11-11 02:11:02 -05:00
proc.c
stats.c FS-Cache: Count the number of initialised operations 2015-04-02 14:28:53 +01:00