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Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt References: From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; 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TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Spam-Flag: NO X-Spam-Score: -3.01 X-Rspamd-Queue-Id: 72C2B33783 X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Level: On 1/23/26 21:12, Lorenzo Stoakes wrote: > We don't actually need to return an output parameter providing mm sequence > number, rather we can separate that out into another function - > __vma_raw_mm_seqnum() - and have any callers which need to obtain that > invoke that instead. > > The access to the raw sequence number requires that we hold the exclusive > mmap lock such that we know we can't race vma_end_write_all(), so move the > assert to __vma_raw_mm_seqnum() to make this requirement clear. > > Also while we're here, convert all of the VM_BUG_ON_VMA()'s to > VM_WARN_ON_ONCE_VMA()'s in line with the convention that we do not invoke > oopses when we can avoid it. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Few nits: > --- > include/linux/mmap_lock.h | 44 ++++++++++++++++++++++----------------- > 1 file changed, 25 insertions(+), 19 deletions(-) > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 678f90080fa6..23bde4bd5a85 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -258,17 +258,30 @@ static inline void vma_end_read(struct vm_area_struct *vma) > vma_refcount_put(vma); > } > > -/* WARNING! Can only be used if mmap_lock is expected to be write-locked */ > -static inline bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq) > +static inline unsigned int __vma_raw_mm_seqnum(struct vm_area_struct *vma) > { > + const struct mm_struct *mm = vma->vm_mm; > + > + /* We must hold an exclusive write lock for this access to be valid. */ > mmap_assert_write_locked(vma->vm_mm); > + return mm->mm_lock_seq.sequence; > +} > > +/* > + * Determine whether a VMA is write-locked. Must be invoked ONLY if the mmap > + * write lock is held. > + * > + * Returns true if write-locked, otherwise false. > + * > + * Note that mm_lock_seq is updated only if the VMA is NOT write-locked. This line is no longer applicable. > + */ > +static inline bool __is_vma_write_locked(struct vm_area_struct *vma) > +{ > /* > * current task is holding mmap_write_lock, both vma->vm_lock_seq and > * mm->mm_lock_seq can't be concurrently modified. > */ > - *mm_lock_seq = vma->vm_mm->mm_lock_seq.sequence; > - return (vma->vm_lock_seq == *mm_lock_seq); > + return vma->vm_lock_seq == __vma_raw_mm_seqnum(vma); > } > > int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq, > @@ -281,12 +294,10 @@ int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq, > */ > static inline void vma_start_write(struct vm_area_struct *vma) > { > - unsigned int mm_lock_seq; > - > - if (__is_vma_write_locked(vma, &mm_lock_seq)) > + if (__is_vma_write_locked(vma)) > return; > > - __vma_start_write(vma, mm_lock_seq, TASK_UNINTERRUPTIBLE); > + __vma_start_write(vma, __vma_raw_mm_seqnum(vma), TASK_UNINTERRUPTIBLE); At this point I think __vma_start_write() could just perform __vma_raw_mm_seqnum() itself and we can remove the param. It could possibly make the inline code smaller.