Milosz Tanski 5a6f282a20 fscache: Netfs function for cleanup post readpages ... Currently the fscache code expect the netfs to call fscache_readpages_or_alloc inside the aops readpages callback. It marks all the pages in the list provided by readahead with PG_private_2. In the cases that the netfs fails to read all the pages (which is legal) it ends up returning to the readahead and triggering a BUG. This happens because the page list still contains marked pages. This patch implements a simple fscache_readpages_cancel function that the netfs should call before returning from readpages. It will revoke the pages from the underlying cache backend and unmark them. The problem was originally worked out in the Ceph devel tree, but it also occurs in CIFS. It appears that NFS, AFS and 9P are okay as read_cache_pages() will clean up the unprocessed pages in the case of an error. This can be used to address the following oops: [12410647.597278] BUG: Bad page state in process petabucket pfn:3d504e [12410647.597292] page:ffffea000f541380 count:0 mapcount:0 mapping: (null) index:0x0 [12410647.597298] page flags: 0x200000000001000(private_2) ... [12410647.597334] Call Trace: [12410647.597345] [<ffffffff815523f2>] dump_stack+0x19/0x1b [12410647.597356] [<ffffffff8111def7>] bad_page+0xc7/0x120 [12410647.597359] [<ffffffff8111e49e>] free_pages_prepare+0x10e/0x120 [12410647.597361] [<ffffffff8111fc80>] free_hot_cold_page+0x40/0x170 [12410647.597363] [<ffffffff81123507>] __put_single_page+0x27/0x30 [12410647.597365] [<ffffffff81123df5>] put_page+0x25/0x40 [12410647.597376] [<ffffffffa02bdcf9>] ceph_readpages+0x2e9/0x6e0 [ceph] [12410647.597379] [<ffffffff81122a8f>] __do_page_cache_readahead+0x1af/0x260 [12410647.597382] [<ffffffff81122ea1>] ra_submit+0x21/0x30 [12410647.597384] [<ffffffff81118f64>] filemap_fault+0x254/0x490 [12410647.597387] [<ffffffff8113a74f>] __do_fault+0x6f/0x4e0 [12410647.597391] [<ffffffff810125bd>] ? __switch_to+0x16d/0x4a0 [12410647.597395] [<ffffffff810865ba>] ? finish_task_switch+0x5a/0xc0 [12410647.597398] [<ffffffff8113d856>] handle_pte_fault+0xf6/0x930 [12410647.597401] [<ffffffff81008c33>] ? pte_mfn_to_pfn+0x93/0x110 [12410647.597403] [<ffffffff81008cce>] ? xen_pmd_val+0xe/0x10 [12410647.597405] [<ffffffff81005469>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [12410647.597407] [<ffffffff8113f361>] handle_mm_fault+0x251/0x370 [12410647.597411] [<ffffffff812b0ac4>] ? call_rwsem_down_read_failed+0x14/0x30 [12410647.597414] [<ffffffff8155bffa>] __do_page_fault+0x1aa/0x550 [12410647.597418] [<ffffffff8108011d>] ? up_write+0x1d/0x20 [12410647.597422] [<ffffffff8113141c>] ? vm_mmap_pgoff+0xbc/0xe0 [12410647.597425] [<ffffffff81143bb8>] ? SyS_mmap_pgoff+0xd8/0x240 [12410647.597427] [<ffffffff8155c3ae>] do_page_fault+0xe/0x10 [12410647.597431] [<ffffffff81558818>] page_fault+0x28/0x30 Signed-off-by: Milosz Tanski <milosz@adfin.com> Signed-off-by: David Howells <dhowells@redhat.com>		2013-09-06 09:17:30 +01:00
..
backend-api.txt	FS-Cache: Add interface to check consistency of a cached object	2013-09-06 09:17:30 +01:00
cachefiles.txt
fscache.txt	fscache: convert object to use workqueue instead of slow-work	2010-07-22 22:58:34 +02:00
netfs-api.txt	fscache: Netfs function for cleanup post readpages	2013-09-06 09:17:30 +01:00
object.txt	FS-Cache: Provide proper invalidation	2012-12-20 22:04:07 +00:00
operations.txt	FS-Cache: Fix operation state management and accounting	2012-12-20 21:58:26 +00:00