kernel/linux.git/fs/netfs/buffered_read.c, branch v6.12.91

netfs: Fix enomem handling in buffered reads

2025-01-17T12:40:34+00:00

[ Upstream commit 105549d09a539a876b7c3330ab52d8aceedad358 ] If netfs_read_to_pagecache() gets an error from either ->prepare_read() or from netfs_prepare_read_iterator(), it needs to decrement ->nr_outstanding, cancel the subrequest and break out of the issuing loop. Currently, it only does this for two of the cases, but there are two more that aren't handled. Fix this by moving the handling to a common place and jumping to it from all four places. This is in preference to inserting a wrapper around netfs_prepare_read_iterator() as proposed by Dmitry Antipov[1]. Link: https://lore.kernel.org/r/20241202093943.227786-1-dmantipov@yandex.ru/ [1] Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") Reported-by: syzbot+404b4b745080b6210c6c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=404b4b745080b6210c6c Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241213135013.2964079-4-dhowells@redhat.com Tested-by: syzbot+404b4b745080b6210c6c@syzkaller.appspotmail.com cc: Dmitry Antipov cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

netfs: In readahead, put the folio refs as soon extracted

2024-10-07T11:48:22+00:00

netfslib currently defers dropping the ref on the folios it obtains during readahead to after it has started I/O on the basis that we can do it whilst we wait for the I/O to complete, but this runs the risk of the I/O collection racing with this in future. Furthermore, Matthew Wilcox strongly suggests that the refs should be dropped immediately, as readahead_folio() does (netfslib is using __readahead_batch() which doesn't drop the refs). Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") Suggested-by: Matthew Wilcox Signed-off-by: David Howells Link: https://lore.kernel.org/r/3771538.1728052438@warthog.procyon.org.uk cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs: Speed up buffered reading

2024-09-12T10:20:41+00:00

Improve the efficiency of buffered reads in a number of ways: (1) Overhaul the algorithm in general so that it's a lot more compact and split the read submission code between buffered and unbuffered versions. The unbuffered version can be vastly simplified. (2) Read-result collection is handed off to a work queue rather than being done in the I/O thread. Multiple subrequests can be processes simultaneously. (3) When a subrequest is collected, any folios it fully spans are collected and "spare" data on either side is donated to either the previous or the next subrequest in the sequence. Notes: (*) Readahead expansion is massively slows down fio, presumably because it causes a load of extra allocations, both folio and xarray, up front before RPC requests can be transmitted. (*) RDMA with cifs does appear to work, both with SIW and RXE. (*) PG_private_2-based reading and copy-to-cache is split out into its own file and altered to use folio_queue. Note that the copy to the cache now creates a new write transaction against the cache and adds the folios to be copied into it. This allows it to use part of the writeback I/O code. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-20-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Fix handling of USE_PGPRIV2 and WRITE_TO_CACHE flags

2024-08-12T20:03:27+00:00

The NETFS_RREQ_USE_PGPRIV2 and NETFS_RREQ_WRITE_TO_CACHE flags aren't used correctly. The problem is that we try to set them up in the request initialisation, but we the cache may be in the process of setting up still, and so the state may not be correct. Further, we secondarily sample the cache state and make contradictory decisions later. The issue arises because we set up the cache resources, which allows the cache's ->prepare_read() to switch on NETFS_SREQ_COPY_TO_CACHE - which triggers cache writing even if we didn't set the flags when allocating. Fix this in the following way: (1) Drop NETFS_ICTX_USE_PGPRIV2 and instead set NETFS_RREQ_USE_PGPRIV2 in ->init_request() rather than trying to juggle that in netfs_alloc_request(). (2) Repurpose NETFS_RREQ_USE_PGPRIV2 to merely indicate that if caching is to be done, then PG_private_2 is to be used rather than only setting it if we decide to cache and then having netfs_rreq_unlock_folios() set the non-PG_private_2 writeback-to-cache if it wasn't set. (3) Split netfs_rreq_unlock_folios() into two functions, one of which contains the deprecated code for using PG_private_2 to avoid accidentally doing the writeback path - and always use it if USE_PGPRIV2 is set. (4) As NETFS_ICTX_USE_PGPRIV2 is removed, make netfs_write_begin() always wait for PG_private_2. This function is deprecated and only used by ceph anyway, and so label it so. (5) Drop the NETFS_RREQ_WRITE_TO_CACHE flag and use fscache_operation_valid() on the cache_resources instead. This has the advantage of picking up the result of netfs_begin_cache_read() and fscache_begin_write_operation() - which are called after the object is initialised and will wait for the cache to come to a usable state. Just reverting ae678317b95e[1] isn't a sufficient fix, so this need to be applied on top of that. Without this as well, things like: rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { and: WARNING: CPU: 13 PID: 3621 at fs/ceph/caps.c:3386 may happen, along with some UAFs due to PG_private_2 not getting used to wait on writeback completion. Fixes: 2ff1e97587f4 ("netfs: Replace PG_fscache by setting folio->private and marking dirty") Reported-by: Max Kellermann Signed-off-by: David Howells cc: Ilya Dryomov cc: Xiubo Li cc: Hristo Venev cc: Jeff Layton cc: Matthew Wilcox cc: ceph-devel@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/3575457.1722355300@warthog.procyon.org.uk/ [1] Link: https://lore.kernel.org/r/1173209.1723152682@warthog.procyon.org.uk Signed-off-by: Christian Brauner

netfs, ceph: Revert "netfs: Remove deprecated use of PG_private_2 as a second writeback flag"

2024-08-12T20:03:27+00:00

This reverts commit ae678317b95e760607c7b20b97c9cd4ca9ed6e1a. Revert the patch that removes the deprecated use of PG_private_2 in netfslib for the moment as Ceph is actually still using this to track data copied to the cache. Fixes: ae678317b95e ("netfs: Remove deprecated use of PG_private_2 as a second writeback flag") Reported-by: Max Kellermann Signed-off-by: David Howells cc: Ilya Dryomov cc: Xiubo Li cc: Jeff Layton cc: Matthew Wilcox cc: ceph-devel@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org https: //lore.kernel.org/r/3575457.1722355300@warthog.procyon.org.uk Signed-off-by: Christian Brauner

netfs: Revert "netfs: Switch debug logging to pr_debug()"

2024-07-24T08:15:37+00:00

Revert commit 163eae0fb0d4c610c59a8de38040f8e12f89fd43 to get back the original operation of the debugging macros. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20240608151352.22860-2-ukleinek@kernel.org Link: https://lore.kernel.org/r/1410685.1721333252@warthog.procyon.org.uk cc: Uwe Kleine-König cc: Christian Brauner cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

Merge tag 'mm-stable-2024-07-21-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-07-22T00:15:46+00:00

Pull MM updates from Andrew Morton: - In the series "mm: Avoid possible overflows in dirty throttling" Jan Kara addresses a couple of issues in the writeback throttling code. These fixes are also targetted at -stable kernels. - Ryusuke Konishi's series "nilfs2: fix potential issues related to reserved inodes" does that. This should actually be in the mm-nonmm-stable tree, along with the many other nilfs2 patches. My bad. - More folio conversions from Kefeng Wang in the series "mm: convert to folio_alloc_mpol()" - Kemeng Shi has sent some cleanups to the writeback code in the series "Add helper functions to remove repeated code and improve readability of cgroup writeback" - Kairui Song has made the swap code a little smaller and a little faster in the series "mm/swap: clean up and optimize swap cache index". - In the series "mm/memory: cleanly support zeropage in vm_insert_page*(), vm_map_pages*() and vmf_insert_mixed()" David Hildenbrand has reworked the rather sketchy handling of the use of the zeropage in MAP_SHARED mappings. I don't see any runtime effects here - more a cleanup/understandability/maintainablity thing. - Dev Jain has improved selftests/mm/va_high_addr_switch.c's handling of higher addresses, for aarch64. The (poorly named) series is "Restructure va_high_addr_switch". - The core TLB handling code gets some cleanups and possible slight optimizations in Bang Li's series "Add update_mmu_tlb_range() to simplify code". - Jane Chu has improved the handling of our fake-an-unrecoverable-memory-error testing feature MADV_HWPOISON in the series "Enhance soft hwpoison handling and injection". - Jeff Johnson has sent a billion patches everywhere to add MODULE_DESCRIPTION() to everything. Some landed in this pull. - In the series "mm: cleanup MIGRATE_SYNC_NO_COPY mode", Kefeng Wang has simplified migration's use of hardware-offload memory copying. - Yosry Ahmed performs more folio API conversions in his series "mm: zswap: trivial folio conversions". - In the series "large folios swap-in: handle refault cases first", Chuanhua Han inches us forward in the handling of large pages in the swap code. This is a cleanup and optimization, working toward the end objective of full support of large folio swapin/out. - In the series "mm,swap: cleanup VMA based swap readahead window calculation", Huang Ying has contributed some cleanups and a possible fixlet to his VMA based swap readahead code. - In the series "add mTHP support for anonymous shmem" Baolin Wang has taught anonymous shmem mappings to use multisize THP. By default this is a no-op - users must opt in vis sysfs controls. Dramatic improvements in pagefault latency are realized. - David Hildenbrand has some cleanups to our remaining use of page_mapcount() in the series "fs/proc: move page_mapcount() to fs/proc/internal.h". - David also has some highmem accounting cleanups in the series "mm/highmem: don't track highmem pages manually". - Build-time fixes and cleanups from John Hubbard in the series "cleanups, fixes, and progress towards avoiding "make headers"". - Cleanups and consolidation of the core pagemap handling from Barry Song in the series "mm: introduce pmd|pte_needs_soft_dirty_wp helpers and utilize them". - Lance Yang's series "Reclaim lazyfree THP without splitting" has reduced the latency of the reclaim of pmd-mapped THPs under fairly common circumstances. A 10x speedup is seen in a microbenchmark. It does this by punting to aother CPU but I guess that's a win unless all CPUs are pegged. - hugetlb_cgroup cleanups from Xiu Jianfeng in the series "mm/hugetlb_cgroup: rework on cftypes". - Miaohe Lin's series "Some cleanups for memory-failure" does just that thing. - Someone other than SeongJae has developed a DAMON feature in Honggyu Kim's series "DAMON based tiered memory management for CXL memory". This adds DAMON features which may be used to help determine the efficiency of our placement of CXL/PCIe attached DRAM. - DAMON user API centralization and simplificatio work in SeongJae Park's series "mm/damon: introduce DAMON parameters online commit function". - In the series "mm: page_type, zsmalloc and page_mapcount_reset()" David Hildenbrand does some maintenance work on zsmalloc - partially modernizing its use of pageframe fields. - Kefeng Wang provides more folio conversions in the series "mm: remove page_maybe_dma_pinned() and page_mkclean()". - More cleanup from David Hildenbrand, this time in the series "mm/memory_hotplug: use PageOffline() instead of PageReserved() for !ZONE_DEVICE". It "enlightens memory hotplug more about PageOffline() pages" and permits the removal of some virtio-mem hacks. - Barry Song's series "mm: clarify folio_add_new_anon_rmap() and __folio_add_anon_rmap()" is a cleanup to the anon folio handling in preparation for mTHP (multisize THP) swapin. - Kefeng Wang's series "mm: improve clear and copy user folio" implements more folio conversions, this time in the area of large folio userspace copying. - The series "Docs/mm/damon/maintaier-profile: document a mailing tool and community meetup series" tells people how to get better involved with other DAMON developers. From SeongJae Park. - A large series ("kmsan: Enable on s390") from Ilya Leoshkevich does that. - David Hildenbrand sends along more cleanups, this time against the migration code. The series is "mm/migrate: move NUMA hinting fault folio isolation + checks under PTL". - Jan Kara has found quite a lot of strangenesses and minor errors in the readahead code. He addresses this in the series "mm: Fix various readahead quirks". - SeongJae Park's series "selftests/damon: test DAMOS tried regions and {min,max}_nr_regions" adds features and addresses errors in DAMON's self testing code. - Gavin Shan has found a userspace-triggerable WARN in the pagecache code. The series "mm/filemap: Limit page cache size to that supported by xarray" addresses this. The series is marked cc:stable. - Chengming Zhou's series "mm/ksm: cmp_and_merge_page() optimizations and cleanup" cleans up and slightly optimizes KSM. - Roman Gushchin has separated the memcg-v1 and memcg-v2 code - lots of code motion. The series (which also makes the memcg-v1 code Kconfigurable) are "mm: memcg: separate legacy cgroup v1 code and put under config option" and "mm: memcg: put cgroup v1-specific memcg data under CONFIG_MEMCG_V1" - Dan Schatzberg's series "Add swappiness argument to memory.reclaim" adds an additional feature to this cgroup-v2 control file. - The series "Userspace controls soft-offline pages" from Jiaqi Yan permits userspace to stop the kernel's automatic treatment of excessive correctable memory errors. In order to permit userspace to monitor and handle this situation. - Kefeng Wang's series "mm: migrate: support poison recover from migrate folio" teaches the kernel to appropriately handle migration from poisoned source folios rather than simply panicing. - SeongJae Park's series "Docs/damon: minor fixups and improvements" does those things. - In the series "mm/zsmalloc: change back to per-size_class lock" Chengming Zhou improves zsmalloc's scalability and memory utilization. - Vivek Kasireddy's series "mm/gup: Introduce memfd_pin_folios() for pinning memfd folios" makes the GUP code use FOLL_PIN rather than bare refcount increments. So these paes can first be moved aside if they reside in the movable zone or a CMA block. - Andrii Nakryiko has added a binary ioctl()-based API to /proc/pid/maps for much faster reading of vma information. The series is "query VMAs from /proc//maps". - In the series "mm: introduce per-order mTHP split counters" Lance Yang improves the kernel's presentation of developer information related to multisize THP splitting. - Michael Ellerman has developed the series "Reimplement huge pages without hugepd on powerpc (8xx, e500, book3s/64)". This permits userspace to use all available huge page sizes. - In the series "revert unconditional slab and page allocator fault injection calls" Vlastimil Babka removes a performance-affecting and not very useful feature from slab fault injection. * tag 'mm-stable-2024-07-21-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (411 commits) mm/mglru: fix ineffective protection calculation mm/zswap: fix a white space issue mm/hugetlb: fix kernel NULL pointer dereference when migrating hugetlb folio mm/hugetlb: fix possible recursive locking detected warning mm/gup: clear the LRU flag of a page before adding to LRU batch mm/numa_balancing: teach mpol_to_str about the balancing mode mm: memcg1: convert charge move flags to unsigned long long alloc_tag: fix page_ext_get/page_ext_put sequence during page splitting lib: reuse page_ext_data() to obtain codetag_ref lib: add missing newline character in the warning message mm/mglru: fix overshooting shrinker memory mm/mglru: fix div-by-zero in vmpressure_calc_level() mm/kmemleak: replace strncpy() with strscpy() mm, page_alloc: put should_fail_alloc_page() back behing CONFIG_FAIL_PAGE_ALLOC mm, slab: put should_failslab() back behind CONFIG_SHOULD_FAILSLAB mm: ignore data-race in __swap_writepage hugetlbfs: ensure generic_hugetlb_get_unmapped_area() returns higher address than mmap_min_addr mm: shmem: rename mTHP shmem counters mm: swap_state: use folio_alloc_mpol() in __read_swap_cache_async() mm/migrate: putback split folios when numa hint migration fails ...

netfs: drop usage of folio_file_pos

2024-07-04T02:29:55+00:00

folio_file_pos is only needed for mixed usage of page cache and swap cache, for pure page cache usage, the caller can just use folio_pos instead. It can't be a swap cache page here. Swap mapping may only call into fs through swap_rw and that is not supported for netfs. So just drop it and use folio_pos instead. Link: https://lkml.kernel.org/r/20240521175854.96038-7-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: David Howells Cc: Jeff Layton Cc: Anna Schumaker Cc: Barry Song Cc: Chao Yu Cc: Chris Li Cc: David Hildenbrand Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Ilya Dryomov Cc: Jaegeuk Kim Cc: Marc Dionne Cc: Matthew Wilcox (Oracle) Cc: Minchan Kim Cc: NeilBrown Cc: Ryan Roberts Cc: Ryusuke Konishi Cc: Trond Myklebust Cc: Xiubo Li Cc: Yosry Ahmed Signed-off-by: Andrew Morton

netfs: Switch debug logging to pr_debug()

2024-06-12T12:25:41+00:00

Instead of inventing a custom way to conditionally enable debugging, just make use of pr_debug(), which also has dynamic debugging facilities and is more likely known to someone who hunts a problem in the netfs code. Also drop the module parameter netfs_debug which didn't have any effect without further source changes. (The variable netfs_debug was only used in #ifdef blocks for cpp vars that don't exist; Note that CONFIG_NETFS_DEBUG isn't settable via kconfig, a variable with that name never existed in the mainline and is probably just taken over (and renamed) from similar custom debug logging implementations.) Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20240608151352.22860-2-ukleinek@kernel.org Signed-off-by: Christian Brauner

netfs: Add some write-side stats and clean up some stat names

2024-05-01T17:07:36+00:00

Add some write-side stats to count buffered writes, buffered writethrough, and writepages calls. Whilst we're at it, clean up the naming on some of the existing stats counters and organise the output into two sets. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org