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2020-11-03afs: Fix incorrect freeing of the ACL passed to the YFS ACL store opDavid Howells
The cleanup for the yfs_store_opaque_acl2_operation calls the wrong function to destroy the ACL content buffer. It's an afs_acl struct, not a yfs_acl struct - and the free function for latter may pass invalid pointers to kfree(). Fix this by using the afs_acl_put() function. The yfs_acl_put() function is then no longer used and can be removed. general protection fault, probably for non-canonical address 0x7ebde00000000: 0000 [#1] SMP PTI ... RIP: 0010:compound_head+0x0/0x11 ... Call Trace: virt_to_cache+0x8/0x51 kfree+0x5d/0x79 yfs_free_opaque_acl+0x16/0x29 afs_put_operation+0x60/0x114 __vfs_setxattr+0x67/0x72 __vfs_setxattr_noperm+0x66/0xe9 vfs_setxattr+0x67/0xce setxattr+0x14e/0x184 __do_sys_fsetxattr+0x66/0x8f do_syscall_64+0x2d/0x3a entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-11-03afs: Fix warning due to unadvanced marshalling pointerDavid Howells
When using the afs.yfs.acl xattr to change an AuriStor ACL, a warning can be generated when the request is marshalled because the buffer pointer isn't increased after adding the last element, thereby triggering the check at the end if the ACL wasn't empty. This just causes something like the following warning, but doesn't stop the call from happening successfully: kAFS: YFS.StoreOpaqueACL2: Request buffer underflow (36<108) Fix this simply by increasing the count prior to the check. Fixes: f5e4546347bc ("afs: Implement YFS ACL setting") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-29afs: Fix dirty-region encoding on ppc32 with 64K pagesDavid Howells
The dirty region bounds stored in page->private on an afs page are 15 bits on a 32-bit box and can, at most, represent a range of up to 32K within a 32K page with a resolution of 1 byte. This is a problem for powerpc32 with 64K pages enabled. Further, transparent huge pages may get up to 2M, which will be a problem for the afs filesystem on all 32-bit arches in the future. Fix this by decreasing the resolution. For the moment, a 64K page will have a resolution determined from PAGE_SIZE. In the future, the page will need to be passed in to the helper functions so that the page size can be assessed and the resolution determined dynamically. Note that this might not be the ideal way to handle this, since it may allow some leakage of undirtied zero bytes to the server's copy in the case of a 3rd-party conflict. Fixing that would require a separately allocated record and is a more complicated fix. Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-10-29afs: Fix afs_invalidatepage to adjust the dirty regionDavid Howells
Fix afs_invalidatepage() to adjust the dirty region recorded in page->private when truncating a page. If the dirty region is entirely removed, then the private data is cleared and the page dirty state is cleared. Without this, if the page is truncated and then expanded again by truncate, zeros from the expanded, but no-longer dirty region may get written back to the server if the page gets laundered due to a conflicting 3rd-party write. It mustn't, however, shorten the dirty region of the page if that page is still mmapped and has been marked dirty by afs_page_mkwrite(), so a flag is stored in page->private to record this. Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-29afs: Alter dirty range encoding in page->privateDavid Howells
Currently, page->private on an afs page is used to store the range of dirtied data within the page, where the range includes the lower bound, but excludes the upper bound (e.g. 0-1 is a range covering a single byte). This, however, requires a superfluous bit for the last-byte bound so that on a 4KiB page, it can say 0-4096 to indicate the whole page, the idea being that having both numbers the same would indicate an empty range. This is unnecessary as the PG_private bit is clear if it's an empty range (as is PG_dirty). Alter the way the dirty range is encoded in page->private such that the upper bound is reduced by 1 (e.g. 0-0 is then specified the same single byte range mentioned above). Applying this to both bounds frees up two bits, one of which can be used in a future commit. This allows the afs filesystem to be compiled on ppc32 with 64K pages; without this, the following warnings are seen: ../fs/afs/internal.h: In function 'afs_page_dirty_to': ../fs/afs/internal.h:881:15: warning: right shift count >= width of type [-Wshift-count-overflow] 881 | return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK; | ^~ ../fs/afs/internal.h: In function 'afs_page_dirty': ../fs/afs/internal.h:886:28: warning: left shift count >= width of type [-Wshift-count-overflow] 886 | return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from; | ^~ Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-29afs: Wrap page->private manipulations in inline functionsDavid Howells
The afs filesystem uses page->private to store the dirty range within a page such that in the event of a conflicting 3rd-party write to the server, we write back just the bits that got changed locally. However, there are a couple of problems with this: (1) I need a bit to note if the page might be mapped so that partial invalidation doesn't shrink the range. (2) There aren't necessarily sufficient bits to store the entire range of data altered (say it's a 32-bit system with 64KiB pages or transparent huge pages are in use). So wrap the accesses in inline functions so that future commits can change how this works. Also move them out of the tracing header into the in-directory header. There's not really any need for them to be in the tracing header. Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-29afs: Fix where page->private is set during writeDavid Howells
In afs, page->private is set to indicate the dirty region of a page. This is done in afs_write_begin(), but that can't take account of whether the copy into the page actually worked. Fix this by moving the change of page->private into afs_write_end(). Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-29afs: Fix page leak on afs_write_begin() failureDavid Howells
Fix the leak of the target page in afs_write_begin() when it fails. Fixes: 15b4650e55e0 ("afs: convert to new aops") Signed-off-by: David Howells <dhowells@redhat.com> cc: Nick Piggin <npiggin@gmail.com>
2020-10-29afs: Fix to take ref on page when PG_private is setDavid Howells
Fix afs to take a ref on a page when it sets PG_private on it and to drop the ref when removing the flag. Note that in afs_write_begin(), a lot of the time, PG_private is already set on a page to which we're going to add some data. In such a case, we leave the bit set and mustn't increment the page count. As suggested by Matthew Wilcox, use attach/detach_page_private() where possible. Fixes: 31143d5d515e ("AFS: implement basic file write support") Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-10-27afs: Fix afs_launder_page to not clear PG_writebackDavid Howells
Fix afs_launder_page() to not clear PG_writeback on the page it is laundering as the flag isn't set in this case. Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-27afs: Fix a use after free in afs_xattr_get_acl()Dan Carpenter
The "op" pointer is freed earlier when we call afs_put_operation(). Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: Colin Ian King <colin.king@canonical.com>
2020-10-27afs: Fix tracing deref-before-checkDavid Howells
The patch dca54a7bbb8c: "afs: Add tracing for cell refcount and active user count" from Oct 13, 2020, leads to the following Smatch complaint: fs/afs/cell.c:596 afs_unuse_cell() warn: variable dereferenced before check 'cell' (see line 592) Fix this by moving the retrieval of the cell debug ID to after the check of the validity of the cell pointer. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Fixes: dca54a7bbb8c ("afs: Add tracing for cell refcount and active user count") Signed-off-by: David Howells <dhowells@redhat.com> cc: Dan Carpenter <dan.carpenter@oracle.com>
2020-10-27afs: Fix copy_file_range()David Howells
The prevention of splice-write without explicit ops made the copy_file_write() syscall to an afs file (as done by the generic/112 xfstest) fail with EINVAL. Fix by using iter_file_splice_write() for afs. Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2020-10-16Merge tag 'afs-fixes-20201016' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs Pull afs updates from David Howells: "A collection of fixes to fix afs_cell struct refcounting, thereby fixing a slew of related syzbot bugs: - Fix the cell tree in the netns to use an rwsem rather than RCU. There seem to be some problems deriving from the use of RCU and a seqlock to walk the rbtree, but it's not entirely clear what since there are several different failures being seen. Changing things to use an rwsem instead makes it more robust. The extra performance derived from using RCU isn't necessary in this case since the only time we're looking up a cell is during mount or when cells are being manually added. - Fix the refcounting by splitting the usage counter into a memory refcount and an active users counter. The usage counter was doing double duty, keeping track of whether a cell is still in use and keeping track of when it needs to be destroyed - but this makes the clean up tricky. Separating these out simplifies the logic. - Fix purging a cell that has an alias. A cell alias pins the cell it's an alias of, but the alias is always later in the list. Trying to purge in a single pass causes rmmod to hang in such a case. - Fix cell removal. If a cell's manager is requeued whilst it's removing itself, the manager will run again and re-remove itself, causing problems in various places. Follow Hillf Danton's suggestion to insert a more terminal state that causes the manager to do nothing post-removal. In additional to the above, two other changes: - Add a tracepoint for the cell refcount and active users count. This helped with debugging the above and may be useful again in future. - Downgrade an assertion to a print when a still-active server is seen during purging. This was happening as a consequence of incomplete cell removal before the servers were cleaned up" * tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: afs: Don't assert on unpurgeable server records afs: Add tracing for cell refcount and active user count afs: Fix cell removal afs: Fix cell purging with aliases afs: Fix cell refcounting by splitting the usage counter afs: Fix rapid cell addition/removal by not using RCU on cells tree
2020-10-16afs: Don't assert on unpurgeable server recordsDavid Howells
Don't give an assertion failure on unpurgeable afs_server records - which kills the thread - but rather emit a trace line when we are purging a record (which only happens during network namespace removal or rmmod) and print a notice of the problem. Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-16afs: Add tracing for cell refcount and active user countDavid Howells
Add a tracepoint to log the cell refcount and active user count and pass in a reason code through various functions that manipulate these counters. Additionally, a helper function, afs_see_cell(), is provided to log interesting places that deal with a cell without actually doing any accounting directly. Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-16afs: Fix cell removalDavid Howells
Fix cell removal by inserting a more final state than AFS_CELL_FAILED that indicates that the cell has been unpublished in case the manager is already requeued and will go through again. The new AFS_CELL_REMOVED state will just immediately leave the manager function. Going through a second time in the AFS_CELL_FAILED state will cause it to try to remove the cell again, potentially leading to the proc list being removed. Fixes: 989782dcdc91 ("afs: Overhaul cell database management") Reported-by: syzbot+b994ecf2b023f14832c1@syzkaller.appspotmail.com Reported-by: syzbot+0e0db88e1eb44a91ae8d@syzkaller.appspotmail.com Reported-by: syzbot+2d0585e5efcd43d113c2@syzkaller.appspotmail.com Reported-by: syzbot+1ecc2f9d3387f1d79d42@syzkaller.appspotmail.com Reported-by: syzbot+18d51774588492bf3f69@syzkaller.appspotmail.com Reported-by: syzbot+a5e4946b04d6ca8fa5f3@syzkaller.appspotmail.com Suggested-by: Hillf Danton <hdanton@sina.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: Hillf Danton <hdanton@sina.com>
2020-10-16afs: Fix cell purging with aliasesDavid Howells
When the afs module is removed, one of the things that has to be done is to purge the cell database. afs_cell_purge() cancels the management timer and then starts the cell manager work item to do the purging. This does a single run through and then assumes that all cells are now purged - but this is no longer the case. With the introduction of alias detection, a later cell in the database can now be holding an active count on an earlier cell (cell->alias_of). The purge scan passes by the earlier cell first, but this can't be got rid of until it has discarded the alias. Ordinarily, afs_unuse_cell() would handle this by setting the management timer to trigger another pass - but afs_set_cell_timer() doesn't do anything if the namespace is being removed (net->live == false). rmmod then hangs in the wait on cells_outstanding in afs_cell_purge(). Fix this by making afs_set_cell_timer() directly queue the cell manager if net->live is false. This causes additional management passes. Queueing the cell manager increments cells_outstanding to make sure the wait won't complete until all cells are destroyed. Fixes: 8a070a964877 ("afs: Detect cell aliases 1 - Cells with root volumes") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-16afs: Fix cell refcounting by splitting the usage counterDavid Howells
Management of the lifetime of afs_cell struct has some problems due to the usage counter being used to determine whether objects of that type are in use in addition to whether anyone might be interested in the structure. This is made trickier by cell objects being cached for a period of time in case they're quickly reused as they hold the result of a setup process that may be slow (DNS lookups, AFS RPC ops). Problems include the cached root volume from alias resolution pinning its parent cell record, rmmod occasionally hanging and occasionally producing assertion failures. Fix this by splitting the count of active users from the struct reference count. Things then work as follows: (1) The cell cache keeps +1 on the cell's activity count and this has to be dropped before the cell can be removed. afs_manage_cell() tries to exchange the 1 to a 0 with the cells_lock write-locked, and if successful, the record is removed from the net->cells. (2) One struct ref is 'owned' by the activity count. That is put when the active count is reduced to 0 (final_destruction label). (3) A ref can be held on a cell whilst it is queued for management on a work queue without confusing the active count. afs_queue_cell() is added to wrap this. (4) The queue's ref is dropped at the end of the management. This is split out into a separate function, afs_manage_cell_work(). (5) The root volume record is put after a cell is removed (at the final_destruction label) rather then in the RCU destruction routine. (6) Volumes hold struct refs, but aren't active users. (7) Both counts are displayed in /proc/net/afs/cells. There are some management function changes: (*) afs_put_cell() now just decrements the refcount and triggers the RCU destruction if it becomes 0. It no longer sets a timer to have the manager do this. (*) afs_use_cell() and afs_unuse_cell() are added to increase and decrease the active count. afs_unuse_cell() sets the management timer. (*) afs_queue_cell() is added to queue a cell with approprate refs. There are also some other fixes: (*) Don't let /proc/net/afs/cells access a cell's vllist if it's NULL. (*) Make sure that candidate cells in lookups are properly destroyed rather than being simply kfree'd. This ensures the bits it points to are destroyed also. (*) afs_dec_cells_outstanding() is now called in cell destruction rather than at "final_destruction". This ensures that cell->net is still valid to the end of the destructor. (*) As a consequence of the previous two changes, move the increment of net->cells_outstanding that was at the point of insertion into the tree to the allocation routine to correctly balance things. Fixes: 989782dcdc91 ("afs: Overhaul cell database management") Signed-off-by: David Howells <dhowells@redhat.com>
2020-10-16afs: Fix rapid cell addition/removal by not using RCU on cells treeDavid Howells
There are a number of problems that are being seen by the rapidly mounting and unmounting an afs dynamic root with an explicit cell and volume specified (which should probably be rejected, but that's a separate issue): What the tests are doing is to look up/create a cell record for the name given and then tear it down again without actually using it to try to talk to a server. This is repeated endlessly, very fast, and the new cell collides with the old one if it's not quick enough to reuse it. It appears (as suggested by Hillf Danton) that the search through the RB tree under a read_seqbegin_or_lock() under RCU conditions isn't safe and that it's not blocking the write_seqlock(), despite taking two passes at it. He suggested that the code should take a ref on the cell it's attempting to look at - but this shouldn't be necessary until we've compared the cell names. It's possible that I'm missing a barrier somewhere. However, using an RCU search for this is overkill, really - we only need to access the cell name in a few places, and they're places where we're may end up sleeping anyway. Fix this by switching to an R/W semaphore instead. Additionally, draw the down_read() call inside the function (renamed to afs_find_cell()) since all the callers were taking the RCU read lock (or should've been[*]). [*] afs_probe_cell_name() should have been, but that doesn't appear to be involved in the bug reports. The symptoms of this look like: general protection fault, probably for non-canonical address 0xf27d208691691fdb: 0000 [#1] PREEMPT SMP KASAN KASAN: maybe wild-memory-access in range [0x93e924348b48fed8-0x93e924348b48fedf] ... RIP: 0010:strncasecmp lib/string.c:52 [inline] RIP: 0010:strncasecmp+0x5f/0x240 lib/string.c:43 afs_lookup_cell_rcu+0x313/0x720 fs/afs/cell.c:88 afs_lookup_cell+0x2ee/0x1440 fs/afs/cell.c:249 afs_parse_source fs/afs/super.c:290 [inline] ... Fixes: 989782dcdc91 ("afs: Overhaul cell database management") Reported-by: syzbot+459a5dce0b4cb70fd076@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> cc: Hillf Danton <hdanton@sina.com> cc: syzkaller-bugs@googlegroups.com
2020-10-13Merge tag 'block-5.10-2020-10-12' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull block updates from Jens Axboe: - Series of merge handling cleanups (Baolin, Christoph) - Series of blk-throttle fixes and cleanups (Baolin) - Series cleaning up BDI, seperating the block device from the backing_dev_info (Christoph) - Removal of bdget() as a generic API (Christoph) - Removal of blkdev_get() as a generic API (Christoph) - Cleanup of is-partition checks (Christoph) - Series reworking disk revalidation (Christoph) - Series cleaning up bio flags (Christoph) - bio crypt fixes (Eric) - IO stats inflight tweak (Gabriel) - blk-mq tags fixes (Hannes) - Buffer invalidation fixes (Jan) - Allow soft limits for zone append (Johannes) - Shared tag set improvements (John, Kashyap) - Allow IOPRIO_CLASS_RT for CAP_SYS_NICE (Khazhismel) - DM no-wait support (Mike, Konstantin) - Request allocation improvements (Ming) - Allow md/dm/bcache to use IO stat helpers (Song) - Series improving blk-iocost (Tejun) - Various cleanups (Geert, Damien, Danny, Julia, Tetsuo, Tian, Wang, Xianting, Yang, Yufen, yangerkun) * tag 'block-5.10-2020-10-12' of git://git.kernel.dk/linux-block: (191 commits) block: fix uapi blkzoned.h comments blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue blk-mq: get rid of the dead flush handle code path block: get rid of unnecessary local variable block: fix comment and add lockdep assert blk-mq: use helper function to test hw stopped block: use helper function to test queue register block: remove redundant mq check block: invoke blk_mq_exit_sched no matter whether have .exit_sched percpu_ref: don't refer to ref->data if it isn't allocated block: ratelimit handle_bad_sector() message blk-throttle: Re-use the throtl_set_slice_end() blk-throttle: Open code __throtl_de/enqueue_tg() blk-throttle: Move service tree validation out of the throtl_rb_first() blk-throttle: Move the list operation after list validation blk-throttle: Fix IO hang for a corner case blk-throttle: Avoid tracking latency if low limit is invalid blk-throttle: Avoid getting the current time if tg->last_finish_time is 0 blk-throttle: Remove a meaningless parameter for throtl_downgrade_state() block: Remove redundant 'return' statement ...
2020-10-08afs: Fix deadlock between writeback and truncateDavid Howells
The afs filesystem has a lock[*] that it uses to serialise I/O operations going to the server (vnode->io_lock), as the server will only perform one modification operation at a time on any given file or directory. This prevents the the filesystem from filling up all the call slots to a server with calls that aren't going to be executed in parallel anyway, thereby allowing operations on other files to obtain slots. [*] Note that is probably redundant for directories at least since i_rwsem is used to serialise directory modifications and lookup/reading vs modification. The server does allow parallel non-modification ops, however. When a file truncation op completes, we truncate the in-memory copy of the file to match - but we do it whilst still holding the io_lock, the idea being to prevent races with other operations. However, if writeback starts in a worker thread simultaneously with truncation (whilst notify_change() is called with i_rwsem locked, writeback pays it no heed), it may manage to set PG_writeback bits on the pages that will get truncated before afs_setattr_success() manages to call truncate_pagecache(). Truncate will then wait for those pages - whilst still inside io_lock: # cat /proc/8837/stack [<0>] wait_on_page_bit_common+0x184/0x1e7 [<0>] truncate_inode_pages_range+0x37f/0x3eb [<0>] truncate_pagecache+0x3c/0x53 [<0>] afs_setattr_success+0x4d/0x6e [<0>] afs_wait_for_operation+0xd8/0x169 [<0>] afs_do_sync_operation+0x16/0x1f [<0>] afs_setattr+0x1fb/0x25d [<0>] notify_change+0x2cf/0x3c4 [<0>] do_truncate+0x7f/0xb2 [<0>] do_sys_ftruncate+0xd1/0x104 [<0>] do_syscall_64+0x2d/0x3a [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 The writeback operation, however, stalls indefinitely because it needs to get the io_lock to proceed: # cat /proc/5940/stack [<0>] afs_get_io_locks+0x58/0x1ae [<0>] afs_begin_vnode_operation+0xc7/0xd1 [<0>] afs_store_data+0x1b2/0x2a3 [<0>] afs_write_back_from_locked_page+0x418/0x57c [<0>] afs_writepages_region+0x196/0x224 [<0>] afs_writepages+0x74/0x156 [<0>] do_writepages+0x2d/0x56 [<0>] __writeback_single_inode+0x84/0x207 [<0>] writeback_sb_inodes+0x238/0x3cf [<0>] __writeback_inodes_wb+0x68/0x9f [<0>] wb_writeback+0x145/0x26c [<0>] wb_do_writeback+0x16a/0x194 [<0>] wb_workfn+0x74/0x177 [<0>] process_one_work+0x174/0x264 [<0>] worker_thread+0x117/0x1b9 [<0>] kthread+0xec/0xf1 [<0>] ret_from_fork+0x1f/0x30 and thus deadlock has occurred. Note that whilst afs_setattr() calls filemap_write_and_wait(), the fact that the caller is holding i_rwsem doesn't preclude more pages being dirtied through an mmap'd region. Fix this by: (1) Use the vnode validate_lock to mediate access between afs_setattr() and afs_writepages(): (a) Exclusively lock validate_lock in afs_setattr() around the whole RPC operation. (b) If WB_SYNC_ALL isn't set on entry to afs_writepages(), trying to shared-lock validate_lock and returning immediately if we couldn't get it. (c) If WB_SYNC_ALL is set, wait for the lock. The validate_lock is also used to validate a file and to zap its cache if the file was altered by a third party, so it's probably a good fit for this. (2) Move the truncation outside of the io_lock in setattr, using the same hook as is used for local directory editing. This requires the old i_size to be retained in the operation record as we commit the revised status to the inode members inside the io_lock still, but we still need to know if we reduced the file size. Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-09-24bdi: initialize ->ra_pages and ->io_pages in bdi_initChristoph Hellwig
Set up a readahead size by default, as very few users have a good reason to change it. This means code, ecryptfs, and orangefs now set up the values while they were previously missing it, while ubifs, mtd and vboxsf manually set it to 0 to avoid readahead. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: David Sterba <dsterba@suse.com> [btrfs] Acked-by: Richard Weinberger <richard@nod.at> [ubifs, mtd] Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-03Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netLinus Torvalds
Pull networking fixes from David Miller: 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi Kivilinna. 2) Fix loss of RTT samples in rxrpc, from David Howells. 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu. 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka. 5) We disable BH for too lokng in sctp_get_port_local(), add a cond_resched() here as well, from Xin Long. 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu. 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from Yonghong Song. 8) Missing of_node_put() in mt7530 DSA driver, from Sumera Priyadarsini. 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan. 10) Fix geneve tunnel checksumming bug in hns3, from Yi Li. 11) Memory leak in rxkad_verify_response, from Dinghao Liu. 12) In tipc, don't use smp_processor_id() in preemptible context. From Tuong Lien. 13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu. 14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter. 15) Fix ABI mismatch between driver and firmware in nfp, from Louis Peens. * git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits) net/smc: fix sock refcounting in case of termination net/smc: reset sndbuf_desc if freed net/smc: set rx_off for SMCR explicitly net/smc: fix toleration of fake add_link messages tg3: Fix soft lockup when tg3_reset_task() fails. doc: net: dsa: Fix typo in config code sample net: dp83867: Fix WoL SecureOn password nfp: flower: fix ABI mismatch between driver and firmware tipc: fix shutdown() of connectionless socket ipv6: Fix sysctl max for fib_multipath_hash_policy drivers/net/wan/hdlc: Change the default of hard_header_len to 0 net: gemini: Fix another missing clk_disable_unprepare() in probe net: bcmgenet: fix mask check in bcmgenet_validate_flow() amd-xgbe: Add support for new port mode net: usb: dm9601: Add USB ID of Keenetic Plus DSL vhost: fix typo in error message net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init() pktgen: fix error message with wrong function name net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode cxgb4: fix thermal zone device registration ...
2020-08-27Merge tag 'rxrpc-fixes-20200820' of ↵David S. Miller
git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs David Howells says: ==================== rxrpc, afs: Fix probing issues Here are some fixes for rxrpc and afs to fix issues in the RTT measuring in rxrpc and thence the Volume Location server probing in afs: (1) Move the serial number of a received ACK into a local variable to simplify the next patch. (2) Fix the loss of RTT samples due to extra interposed ACKs causing baseline information to be discarded too early. This is a particular problem for afs when it sends a single very short call to probe a server it hasn't talked to recently. (3) Fix rxrpc_kernel_get_srtt() to indicate whether it actually has seen any valid samples or not. (4) Remove a field that's set/woken, but never read/waited on. (5) Expose the RTT and other probe information through procfs to make debugging of this stuff easier. (6) Fix VL rotation in afs to only use summary information from VL probing and not the probe running state (which gets clobbered when next a probe is issued). (7) Fix VL rotation to actually return the error aggregated from the probe errors. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
2020-08-27afs: Remove erroneous fallthough annotationDan Carpenter
The fall through annotation comes after a return statement so it's not reachable. Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-23treewide: Use fallthrough pseudo-keywordGustavo A. R. Silva
Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-21afs: Fix NULL deref in afs_dynroot_depopulate()David Howells
If an error occurs during the construction of an afs superblock, it's possible that an error occurs after a superblock is created, but before we've created the root dentry. If the superblock has a dynamic root (ie. what's normally mounted on /afs), the afs_kill_super() will call afs_dynroot_depopulate() to unpin any created dentries - but this will oops if the root hasn't been created yet. Fix this by skipping that bit of code if there is no root dentry. This leads to an oops looking like: general protection fault, ... KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] ... RIP: 0010:afs_dynroot_depopulate+0x25f/0x529 fs/afs/dynroot.c:385 ... Call Trace: afs_kill_super+0x13b/0x180 fs/afs/super.c:535 deactivate_locked_super+0x94/0x160 fs/super.c:335 afs_get_tree+0x1124/0x1460 fs/afs/super.c:598 vfs_get_tree+0x89/0x2f0 fs/super.c:1547 do_new_mount fs/namespace.c:2875 [inline] path_mount+0x1387/0x2070 fs/namespace.c:3192 do_mount fs/namespace.c:3205 [inline] __do_sys_mount fs/namespace.c:3413 [inline] __se_sys_mount fs/namespace.c:3390 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 which is oopsing on this line: inode_lock(root->d_inode); presumably because sb->s_root was NULL. Fixes: 0da0b7fd73e4 ("afs: Display manually added cells in dynamic root mount") Reported-by: syzbot+c1eff8205244ae7e11a6@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-20afs: Fix key ref leak in afs_put_operation()David Howells
The afs_put_operation() function needs to put the reference to the key that's authenticating the operation. Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Reported-by: Dave Botsch <botsch@cnf.cornell.edu> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-20afs: Fix error handling in VL server rotationDavid Howells
The error handling in the VL server rotation in the case of there being no contactable servers is not correct. In such a case, the records of all the servers in the list are scanned and the errors and abort codes are mapped and prioritised and one error is chosen. This is then forgotten and the default error is used (EDESTADDRREQ). Fix this by using the calculated error. Also we need to note whether a server responded on one of its endpoints so that we can priorise an error from an abort message over local and network errors. Fixes: 4584ae96ae30 ("afs: Fix missing net error handling") Signed-off-by: David Howells <dhowells@redhat.com>
2020-08-20afs: Don't use VL probe running state to make decisions outside probe codeDavid Howells
Don't use the running state for VL server probes to make decisions about which server to use as the state is cleared at the start of a probe and intermediate values might also be misleading. Instead, add a separate 'latest known' rtt in the afs_vlserver struct and a flag to indicate if the server is known to be responding and update these as and when we know what to change them to. Fixes: 3bf0fb6f33dd ("afs: Probe multiple fileservers simultaneously") Signed-off-by: David Howells <dhowells@redhat.com>
2020-08-20afs: Expose information from afs_vlserver through /proc for debuggingDavid Howells
Convert various bitfields in afs_vlserver::probe to a mask and then expose this and some other bits of information through /proc/net/afs/<cell>/vlservers to make it easier to debug VL server communication issues. Signed-off-by: David Howells <dhowells@redhat.com>
2020-08-20afs: Remove afs_vlserver->probe.have_resultDavid Howells
Remove afs_vlserver->probe.have_result as it's neither read nor waited upon. Fixes: 3bf0fb6f33dd ("afs: Probe multiple fileservers simultaneously") Signed-off-by: David Howells <dhowells@redhat.com>
2020-08-20rxrpc: Make rxrpc_kernel_get_srtt() indicate validityDavid Howells
Fix rxrpc_kernel_get_srtt() to indicate the validity of the returned smoothed RTT. If we haven't had any valid samples yet, the SRTT isn't useful. Fixes: c410bf01933e ("rxrpc: Fix the excessive initial retransmission timeout") Signed-off-by: David Howells <dhowells@redhat.com>
2020-08-04Merge tag 'uninit-macro-v5.9-rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull uninitialized_var() macro removal from Kees Cook: "This is long overdue, and has hidden too many bugs over the years. The series has several "by hand" fixes, and then a trivial treewide replacement. - Clean up non-trivial uses of uninitialized_var() - Update documentation and checkpatch for uninitialized_var() removal - Treewide removal of uninitialized_var()" * tag 'uninit-macro-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: compiler: Remove uninitialized_var() macro treewide: Remove uninitialized_var() usage checkpatch: Remove awareness of uninitialized_var() macro mm/debug_vm_pgtable: Remove uninitialized_var() usage f2fs: Eliminate usage of uninitialized_var() macro media: sur40: Remove uninitialized_var() usage KVM: PPC: Book3S PR: Remove uninitialized_var() usage clk: spear: Remove uninitialized_var() usage clk: st: Remove uninitialized_var() usage spi: davinci: Remove uninitialized_var() usage ide: Remove uninitialized_var() usage rtlwifi: rtl8192cu: Remove uninitialized_var() usage b43: Remove uninitialized_var() usage drbd: Remove uninitialized_var() usage x86/mm/numa: Remove uninitialized_var() usage docs: deprecated.rst: Add uninitialized_var()
2020-07-16treewide: Remove uninitialized_var() usageKees Cook
Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. In preparation for removing[2] the[3] macro[4], remove all remaining needless uses with the following script: git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \ xargs perl -pi -e \ 's/\buninitialized_var\(([^\)]+)\)/\1/g; s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;' drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid pathological white-space. No outstanding warnings were found building allmodconfig with GCC 9.3.0 for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64, alpha, and m68k. [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5 Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs Signed-off-by: Kees Cook <keescook@chromium.org>
2020-07-15afs: Fix interruption of operationsDavid Howells
The afs filesystem driver allows unstarted operations to be cancelled by signal, but most of these can easily be restarted (mkdir for example). The primary culprits for reproducing this are those applications that use SIGALRM to display a progress counter. File lock-extension operation is marked uninterruptible as we have a limited time in which to do it, and the release op is marked uninterruptible also as if we fail to unlock a file, we'll have to wait 20 mins before anyone can lock it again. The store operation logs a warning if it gets interruption, e.g.: kAFS: Unexpected error from FS.StoreData -4 because it's run from the background - but it can also be run from fdatasync()-type things. However, store options aren't marked interruptible at the moment. Fix this in the following ways: (1) Mark store operations as uninterruptible. It might make sense to relax this for certain situations, but I'm not sure how to make sure that background store ops aren't affected by signals to foreground processes that happen to trigger them. (2) In afs_get_io_locks(), where we're getting the serialisation lock for talking to the fileserver, return ERESTARTSYS rather than EINTR because a lot of the operations (e.g. mkdir) are restartable if we haven't yet started sending the op to the server. Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-27afs: Fix storage of cell namesDavid Howells
The cell name stored in the afs_cell struct is a 64-char + NUL buffer - when it needs to be able to handle up to AFS_MAXCELLNAME (256 chars) + NUL. Fix this by changing the array to a pointer and allocating the string. Found using Coverity. Fixes: 989782dcdc91 ("afs: Overhaul cell database management") Reported-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-20afs: Fix hang on rmmod due to outstanding timerDavid Howells
The fileserver probe timer, net->fs_probe_timer, isn't cancelled when the kafs module is being removed and so the count it holds on net->servers_outstanding doesn't get dropped.. This causes rmmod to wait forever. The hung process shows a stack like: afs_purge_servers+0x1b5/0x23c [kafs] afs_net_exit+0x44/0x6e [kafs] ops_exit_list+0x72/0x93 unregister_pernet_operations+0x14c/0x1ba unregister_pernet_subsys+0x1d/0x2a afs_exit+0x29/0x6f [kafs] __do_sys_delete_module.isra.0+0x1a2/0x24b do_syscall_64+0x51/0x95 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix this by: (1) Attempting to cancel the probe timer and, if successful, drop the count that the timer was holding. (2) Make the timer function just drop the count and not schedule the prober if the afs portion of net namespace is being destroyed. Also, whilst we're at it, make the following changes: (3) Initialise net->servers_outstanding to 1 and decrement it before waiting on it so that it doesn't generate wake up events by being decremented to 0 until we're cleaning up. (4) Switch the atomic_dec() on ->servers_outstanding for ->fs_timer in afs_purge_servers() to use the helper function for that. Fixes: f6cbb368bcb0 ("afs: Actively poll fileservers to maintain NAT or firewall openings") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-20afs: Fix afs_do_lookup() to call correct fetch-status op variantDavid Howells
Fix afs_do_lookup()'s fallback case for when FS.InlineBulkStatus isn't supported by the server. In the fallback, it calls FS.FetchStatus for the specific vnode it's meant to be looking up. Commit b6489a49f7b7 broke this by renaming one of the two identically-named afs_fetch_status_operation descriptors to something else so that one of them could be made non-static. The site that used the renamed one, however, wasn't renamed and didn't produce any warning because the other was declared in a header. Fix this by making afs_do_lookup() use the renamed variant. Note that there are two variants of the success method because one is called from ->lookup() where we may or may not have an inode, but can't call iget until after we've talked to the server - whereas the other is called from within iget where we have an inode, but it may or may not be initialised. The latter variant expects there to be an inode, but because it's being called from there former case, there might not be - resulting in an oops like the following: BUG: kernel NULL pointer dereference, address: 00000000000000b0 ... RIP: 0010:afs_fetch_status_success+0x27/0x7e ... Call Trace: afs_wait_for_operation+0xda/0x234 afs_do_lookup+0x2fe/0x3c1 afs_lookup+0x3c5/0x4bd __lookup_slow+0xcd/0x10f walk_component+0xa2/0x10c path_lookupat.isra.0+0x80/0x110 filename_lookup+0x81/0x104 vfs_statx+0x76/0x109 __do_sys_newlstat+0x39/0x6b do_syscall_64+0x4c/0x78 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: b6489a49f7b7 ("afs: Fix silly rename") Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-16afs: Fix silly renameDavid Howells
Fix AFS's silly rename by the following means: (1) Set the destination directory in afs_do_silly_rename() so as to avoid misbehaviour and indicate that the directory data version will increment by 1 so as to avoid warnings about unexpected changes in the DV. Also indicate that the ctime should be updated to avoid xfstest grumbling. (2) Note when the server indicates that a directory changed more than we expected (AFS_OPERATION_DIR_CONFLICT), indicating a conflict with a third party change, checking on successful completion of unlink and rename. The problem is that the FS.RemoveFile RPC op doesn't report the status of the unlinked file, though YFS.RemoveFile2 does. This can be mitigated by the assumption that if the directory DV cranked by exactly 1, we can be sure we removed one link from the file; further, ordinarily in AFS, files cannot be hardlinked across directories, so if we reduce nlink to 0, the file is deleted. However, if the directory DV jumps by more than 1, we cannot know if a third party intervened by adding or removing a link on the file we just removed a link from. The same also goes for any vnode that is at the destination of the FS.Rename RPC op. (3) Make afs_vnode_commit_status() apply the nlink drop inside the cb_lock section along with the other attribute updates if ->op_unlinked is set on the descriptor for the appropriate vnode. (4) Issue a follow up status fetch to the unlinked file in the event of a third party conflict that makes it impossible for us to know if we actually deleted the file or not. (5) Provide a flag, AFS_VNODE_SILLY_DELETED, to make afs_getattr() lie to the user about the nlink of a silly deleted file so that it appears as 0, not 1. Found with the generic/035 and generic/084 xfstests. Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Reported-by: Marc Dionne <marc.dionne@auristor.com> Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-16afs: afs_vnode_commit_status() doesn't need to check the RPC errorDavid Howells
afs_vnode_commit_status() is only ever called if op->error is 0, so remove the op->error checks from the function. Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-16afs: Fix use of afs_check_for_remote_deletion()David Howells
afs_check_for_remote_deletion() checks to see if error ENOENT is returned by the server in response to an operation and, if so, marks the primary vnode as having been deleted as the FID is no longer valid. However, it's being called from the operation success functions, where no abort has happened - and if an inline abort is recorded, it's handled by afs_vnode_commit_status(). Fix this by actually calling the operation aborted method if provided and having that point to afs_check_for_remote_deletion(). Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-16afs: Remove afs_operation::abort_codeDavid Howells
Remove afs_operation::abort_code as it's read but never set. Use ac.abort_code instead. Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-16afs: Fix yfs_fs_fetch_status() to honour vnode selectorDavid Howells
Fix yfs_fs_fetch_status() to honour the vnode selector in op->fetch_status.which as does afs_fs_fetch_status() that allows afs_do_lookup() to use this as an alternative to the InlineBulkStatus RPC call if not implemented by the server. This doesn't matter in the current code as YFS servers always implement InlineBulkStatus, but a subsequent will call it on YFS servers too in some circumstances. Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-16afs: Remove yfs_fs_fetch_file_status() as it's not usedDavid Howells
Remove yfs_fs_fetch_file_status() as it's no longer used. Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-15afs: Fix the mapping of the UAEOVERFLOW abort codeDavid Howells
Abort code UAEOVERFLOW is returned when we try and set a time that's out of range, but it's currently mapped to EREMOTEIO by the default case. Fix UAEOVERFLOW to map instead to EOVERFLOW. Found with the generic/258 xfstest. Note that the test is wrong as it assumes that the filesystem will support a pre-UNIX-epoch date. Fixes: 1eda8bab70ca ("afs: Add support for the UAE error table") Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-15afs: Fix truncation issues and mmap writeback sizeDavid Howells
Fix the following issues: (1) Fix writeback to reduce the size of a store operation to i_size, effectively discarding the extra data. The problem comes when afs_page_mkwrite() records that a page is about to be modified by mmap(). It doesn't know what bits of the page are going to be modified, so it records the whole page as being dirty (this is stored in page->private as start and end offsets). Without this, the marshalling for the store to the server extends the size of the file to the end of the page (in afs_fs_store_data() and yfs_fs_store_data()). (2) Fix setattr to actually truncate the pagecache, thereby clearing the discarded part of a file. (3) Fix setattr to check that the new size is okay and to disable ATTR_SIZE if i_size wouldn't change. (4) Force i_size to be updated as the result of a truncate. (5) Don't truncate if ATTR_SIZE is not set. (6) Call pagecache_isize_extended() if the file was enlarged. Note that truncate_set_size() isn't used because the setting of i_size is done inside afs_vnode_commit_status() under the vnode->cb_lock. Found with the generic/029 and generic/393 xfstests. Fixes: 31143d5d515e ("AFS: implement basic file write support") Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record") Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-15afs: Concoct ctimesDavid Howells
The in-kernel afs filesystem ignores ctime because the AFS fileserver protocol doesn't support ctimes. This, however, causes various xfstests to fail. Work around this by: (1) Setting ctime to attr->ia_ctime in afs_setattr(). (2) Not ignoring ATTR_MTIME_SET, ATTR_TIMES_SET and ATTR_TOUCH settings. (3) Setting the ctime from the server mtime when on the target file when creating a hard link to it. (4) Setting the ctime on directories from their revised mtimes when renaming/moving a file. Found by the generic/221 and generic/309 xfstests. Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-15afs: Fix EOF corruptionDavid Howells
When doing a partial writeback, afs_write_back_from_locked_page() may generate an FS.StoreData RPC request that writes out part of a file when a file has been constructed from pieces by doing seek, write, seek, write, ... as is done by ld. The FS.StoreData RPC is given the current i_size as the file length, but the server basically ignores it unless the data length is 0 (in which case it's just a truncate operation). The revised file length returned in the result of the RPC may then not reflect what we suggested - and this leads to i_size getting moved backwards - which causes issues later. Fix the client to take account of this by ignoring the returned file size unless the data version number jumped unexpectedly - in which case we're going to have to clear the pagecache and reload anyway. This can be observed when doing a kernel build on an AFS mount. The following pair of commands produce the issue: ld -m elf_x86_64 -z max-page-size=0x200000 --emit-relocs \ -T arch/x86/realmode/rm/realmode.lds \ arch/x86/realmode/rm/header.o \ arch/x86/realmode/rm/trampoline_64.o \ arch/x86/realmode/rm/stack.o \ arch/x86/realmode/rm/reboot.o \ -o arch/x86/realmode/rm/realmode.elf arch/x86/tools/relocs --realmode \ arch/x86/realmode/rm/realmode.elf \ >arch/x86/realmode/rm/realmode.relocs This results in the latter giving: Cannot read ELF section headers 0/18: Success as the realmode.elf file got corrupted. The sequence of events can also be driven with: xfs_io -t -f \ -c "pwrite -S 0x58 0 0x58" \ -c "pwrite -S 0x59 10000 1000" \ -c "close" \ /afs/example.com/scratch/a Fixes: 31143d5d515e ("AFS: implement basic file write support") Signed-off-by: David Howells <dhowells@redhat.com>