kernel/linux.git/fs/dax.c, branch v5.10.257

fsdax: mark the iomap argument to dax_iomap_sector as const

2025-12-06T21:08:18+00:00

[ Upstream commit 7e4f4b2d689d959b03cb07dfbdb97b9696cb1076 ] Signed-off-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Signed-off-by: Eliav Farber Signed-off-by: Sasha Levin

fsdax: Fix infinite loop in dax_iomap_rw()

2025-10-29T13:01:25+00:00

commit 17d9c15c9b9e7fb285f7ac5367dfb5f00ff575e3 upstream. I got an infinite loop and a WARNING report when executing a tail command in virtiofs. WARNING: CPU: 10 PID: 964 at fs/iomap/iter.c:34 iomap_iter+0x3a2/0x3d0 Modules linked in: CPU: 10 PID: 964 Comm: tail Not tainted 5.19.0-rc7 Call Trace: dax_iomap_rw+0xea/0x620 ? __this_cpu_preempt_check+0x13/0x20 fuse_dax_read_iter+0x47/0x80 fuse_file_read_iter+0xae/0xd0 new_sync_read+0xfe/0x180 ? 0xffffffff81000000 vfs_read+0x14d/0x1a0 ksys_read+0x6d/0xf0 __x64_sys_read+0x1a/0x20 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd The tail command will call read() with a count of 0. In this case, iomap_iter() will report this WARNING, and always return 1 which casuing the infinite loop in dax_iomap_rw(). Fixing by checking count whether is 0 in dax_iomap_rw(). Fixes: ca289e0b95af ("fsdax: switch dax_iomap_rw to use iomap_iter") Signed-off-by: Li Jinlin Reviewed-by: Darrick J. Wong Link: https://lore.kernel.org/r/20220725032050.3873372-1-lijinlin3@huawei.com Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

dax: skip read lock assertion for read-only filesystems

2025-10-29T13:01:18+00:00

[ Upstream commit 154d1e7ad9e5ce4b2aaefd3862b3dba545ad978d ] The commit 168316db3583("dax: assert that i_rwsem is held exclusive for writes") added lock assertions to ensure proper locking in DAX operations. However, these assertions trigger false-positive lockdep warnings since read lock is unnecessary on read-only filesystems(e.g., erofs). This patch skips the read lock assertion for read-only filesystems, eliminating the spurious warnings while maintaining the integrity checks for writable filesystems. Fixes: 168316db3583 ("dax: assert that i_rwsem is held exclusive for writes") Signed-off-by: Yuezhang Mo Reviewed-by: Friendy Su Reviewed-by: Daniel Palmer Reviewed-by: Gao Xiang Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

fsdax: switch dax_iomap_rw to use iomap_iter

2025-10-29T13:01:18+00:00

[ Upstream commit ca289e0b95afa973d204c77a4ad5c37e06145fbf ] Switch the dax_iomap_rw implementation to use iomap_iter. Signed-off-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Stable-dep-of: 154d1e7ad9e5 ("dax: skip read lock assertion for read-only filesystems") Signed-off-by: Sasha Levin

dax: fix cache flush on PMD-mapped pages

2022-06-09T08:21:16+00:00

[ Upstream commit e583b5c472bd23d450e06f148dc1f37be74f7666 ] The flush_cache_page() only remove a PAGE_SIZE sized range from the cache. However, it does not cover the full pages in a THP except a head page. Replace it with flush_cache_range() to fix this issue. This is just a documentation issue with the respect to properly documenting the expected usage of cache flushing before modifying the pmd. However, in practice this is not a problem due to the fact that DAX is not available on architectures with virtually indexed caches per: commit d92576f1167c ("dax: does not work correctly with virtual aliasing caches") Link: https://lkml.kernel.org/r/20220403053957.10770-3-songmuchun@bytedance.com Fixes: f729c8c9b24f ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean") Signed-off-by: Muchun Song Reviewed-by: Dan Williams Reviewed-by: Christoph Hellwig Cc: Alistair Popple Cc: Al Viro Cc: Hugh Dickins Cc: Jan Kara Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Cc: Ralph Campbell Cc: Ross Zwisler Cc: Xiongchun Duan Cc: Xiyu Yang Cc: Yang Shi Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin

dax: fix ENOMEM handling in grab_mapping_entry()

2021-07-14T14:56:13+00:00

[ Upstream commit 1a14e3779dd58c16b30e56558146e5cc850ba8b0 ] grab_mapping_entry() has a bug in handling of ENOMEM condition. Suppose we have a PMD entry at index i which we are downgrading to a PTE entry. grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear the entry in xarray, and decrement mapping->nrpages. The it will call: entry = dax_make_entry(pfn_to_pfn_t(0), flags); dax_lock_entry(xas, entry); which inserts new PTE entry into xarray. However this may fail allocating the new node. We handle this by: if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM)) goto retry; however pmd_downgrade stays set to true even though 'entry' returned from get_unlocked_entry() will be NULL now. And we will go again through the downgrade branch. This is mostly harmless except that mapping->nrpages is decremented again and we temporarily have an invalid entry stored in xarray. Fix the problem by setting pmd_downgrade to false each time we lookup the entry we work with so that it matches the entry we found. Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz Fixes: b15cd800682f ("dax: Convert page fault handlers to XArray") Signed-off-by: Jan Kara Reviewed-by: Dan Williams Cc: Matthew Wilcox Cc: "Aneesh Kumar K.V" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

dax: Wake up all waiters after invalidating dax entry

2021-05-19T08:13:12+00:00

[ Upstream commit 237388320deffde7c2d65ed8fc9eef670dc979b3 ] I am seeing missed wakeups which ultimately lead to a deadlock when I am using virtiofs with DAX enabled and running "make -j". I had to mount virtiofs as rootfs and also reduce to dax window size to 256M to reproduce the problem consistently. So here is the problem. put_unlocked_entry() wakes up waiters only if entry is not null as well as !dax_is_conflict(entry). But if I call multiple instances of invalidate_inode_pages2() in parallel, then I can run into a situation where there are waiters on this index but nobody will wake these waiters. invalidate_inode_pages2() invalidate_inode_pages2_range() invalidate_exceptional_entry2() dax_invalidate_mapping_entry_sync() __dax_invalidate_entry() { xas_lock_irq(&xas); entry = get_unlocked_entry(&xas, 0); ... ... dax_disassociate_entry(entry, mapping, trunc); xas_store(&xas, NULL); ... ... put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); } Say a fault in in progress and it has locked entry at offset say "0x1c". Now say three instances of invalidate_inode_pages2() are in progress (A, B, C) and they all try to invalidate entry at offset "0x1c". Given dax entry is locked, all tree instances A, B, C will wait in wait queue. When dax fault finishes, say A is woken up. It will store NULL entry at index "0x1c" and wake up B. When B comes along it will find "entry=0" at page offset 0x1c and it will call put_unlocked_entry(&xas, 0). And this means put_unlocked_entry() will not wake up next waiter, given the current code. And that means C continues to wait and is not woken up. This patch fixes the issue by waking up all waiters when a dax entry has been invalidated. This seems to fix the deadlock I am facing and I can make forward progress. Reported-by: Sergio Lopez Fixes: ac401cc78242 ("dax: New fault locking") Reviewed-by: Jan Kara Suggested-by: Dan Williams Signed-off-by: Vivek Goyal Link: https://lore.kernel.org/r/20210428190314.1865312-4-vgoyal@redhat.com Signed-off-by: Dan Williams Signed-off-by: Sasha Levin

dax: Add a wakeup mode parameter to put_unlocked_entry()

2021-05-19T08:13:12+00:00

[ Upstream commit 4c3d043d271d4d629aa2328796cdfc96b37d3b3c ] As of now put_unlocked_entry() always wakes up next waiter. In next patches we want to wake up all waiters at one callsite. Hence, add a parameter to the function. This patch does not introduce any change of behavior. Reviewed-by: Greg Kurz Reviewed-by: Jan Kara Suggested-by: Dan Williams Signed-off-by: Vivek Goyal Link: https://lore.kernel.org/r/20210428190314.1865312-3-vgoyal@redhat.com Signed-off-by: Dan Williams Signed-off-by: Sasha Levin

dax: Add an enum for specifying dax wakup mode

2021-05-19T08:13:12+00:00

[ Upstream commit 698ab77aebffe08b312fbcdddeb0e8bd08b78717 ] Dan mentioned that he is not very fond of passing around a boolean true/false to specify if only next waiter should be woken up or all waiters should be woken up. He instead prefers that we introduce an enum and make it very explicity at the callsite itself. Easier to read code. This patch should not introduce any change of behavior. Reviewed-by: Greg Kurz Reviewed-by: Jan Kara Suggested-by: Dan Williams Signed-off-by: Vivek Goyal Link: https://lore.kernel.org/r/20210428190314.1865312-2-vgoyal@redhat.com Signed-off-by: Dan Williams Signed-off-by: Sasha Levin

mm: provide a saner PTE walking API for modules

2021-02-26T09:13:01+00:00

commit 9fd6dad1261a541b3f5fa7dc5b152222306e6702 upstream. Currently, the follow_pfn function is exported for modules but follow_pte is not. However, follow_pfn is very easy to misuse, because it does not provide protections (so most of its callers assume the page is writable!) and because it returns after having already unlocked the page table lock. Provide instead a simplified version of follow_pte that does not have the pmdpp and range arguments. The older version survives as follow_invalidate_pte() for use by fs/dax.c. Reviewed-by: Jason Gunthorpe Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman