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 ApT1pAXq 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001389, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 05, 2025 at 12:50:25PM +0100, Vlastimil Babka wrote: > On 3/3/25 12:08, Lorenzo Stoakes wrote: > > Consider the case of a a partial mremap() (that results in a VMA split) of > > an accountable VMA (i.e. which has the VM_ACCOUNT flag set) whose start > > address is zero, with the MREMAP_MAYMOVE flag specified and a scenario > > where a move does in fact occur: > > > > addr end > > | | > > v v > > |-------------| > > | vma | > > |-------------| > > 0 > > > > This move is affected by unmapping the range [addr, end). In order to > > prevent an incorrect decrement of accounted memory which has already been > > determined, the mremap() code in move_vma() clears VM_ACCOUNT from the VMA > > prior to doing so, before reestablishing it in each of the VMAs post-split: > > > > addr end > > | | > > v v > > |---| |---| > > | A | | B | > > |---| |---| > > > > Commit 6b73cff239e5 ("mm: change munmap splitting order and move_vma()") > > changed this logic such as to determine whether there is a need to do so by > > establishing account_start and account_end and, in the instance where such > > an operation is required, assigning them to vma->vm_start and vma->vm_end. > > > > Later the code checks if the operation is required for 'A' referenced above > > thusly: > > > > if (account_start) { > > ... > > } > > > > However, if the VMA described above has vma->vm_start == 0, which is now > > assigned to account_start, this branch will not be executed. > > > > As a result, the VMA 'A' above will remain stripped of its VM_ACCOUNT flag, > > incorrectly. > > > > The fix is to simply convert these variables to booleans and set them as > > required. > > > > Signed-off-by: Lorenzo Stoakes > > Fixes: 6b73cff239e5 ("mm: change munmap splitting order and move_vma()") > > Cc: stable@vger.kernel.org > > Looks like the variables would be more accurately named account_prev and > account_next? But maybe it's refactored later anyway. Keeps the diff to > stable backport smaller. Yeah indeed, I think it's better to keep it relatively smaller. > > Reviewed-by: Vlastimil Babka > Thanks!