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mm/mremap: put VMA check and prep logic into helper function

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Rather than lumping everything together in do_mremap(), add a new helper
function, check_prep_vma(), to do the work relating to each VMA.

This further lays groundwork for subsequent patches which will allow for
batched VMA mremap().

Additionally, if we set vrm->new_addr == vrm->addr when prepping the VMA,
this avoids us needing to do so in the expand VMA mlocked case.

No functional change intended.

Link: https://lkml.kernel.org/r/15efa3c57935f7f8894094b94c1803c2f322c511.1752770784.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2025-07-17 17:55:53 +01:00
committed by Andrew Morton
parent 3215eaceca
commit f256a7a4ca
1 changed files with 28 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files

58
mm/mremap.c
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@@ -1634,7 +1634,6 @@ static bool align_hugetlb(struct vma_remap_struct *vrm)
static unsigned long expand_vma(struct vma_remap_struct *vrm)
{
unsigned long err;
unsigned long addr = vrm->addr;
err = remap_is_valid(vrm);
if (err)
@@ -1649,16 +1648,8 @@ static unsigned long expand_vma(struct vma_remap_struct *vrm)
if (err)
return err;
/*
* We want to populate the newly expanded portion of the VMA to
* satisfy the expectation that mlock()'ing a VMA maintains all
* of its pages in memory.
*/
if (vrm->mlocked)
vrm->new_addr = addr;
/* OK we're done! */
return addr;
return vrm->addr;
}
/*
@@ -1714,10 +1705,33 @@ static unsigned long mremap_at(struct vma_remap_struct *vrm)
return -EINVAL;
}
static int check_prep_vma(struct vma_remap_struct *vrm)
{
struct vm_area_struct *vma = vrm->vma;
if (!vma)
return -EFAULT;
/* If mseal()'d, mremap() is prohibited. */
if (!can_modify_vma(vma))
return -EPERM;
/* Align to hugetlb page size, if required. */
if (is_vm_hugetlb_page(vma) && !align_hugetlb(vrm))
return -EINVAL;
vrm_set_delta(vrm);
vrm->remap_type = vrm_remap_type(vrm);
/* For convenience, we set new_addr even if VMA won't move. */
if (!vrm_implies_new_addr(vrm))
vrm->new_addr = vrm->addr;
return 0;
}
static unsigned long do_mremap(struct vma_remap_struct *vrm)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long res;
vrm->old_len = PAGE_ALIGN(vrm->old_len);
@@ -1731,26 +1745,10 @@ static unsigned long do_mremap(struct vma_remap_struct *vrm)
return -EINTR;
vrm->mmap_locked = true;
vma = vrm->vma = vma_lookup(mm, vrm->addr);
if (!vma) {
res = -EFAULT;
vrm->vma = vma_lookup(current->mm, vrm->addr);
res = check_prep_vma(vrm);
if (res)
goto out;
}
/* If mseal()'d, mremap() is prohibited. */
if (!can_modify_vma(vma)) {
res = -EPERM;
goto out;
}
/* Align to hugetlb page size, if required. */
if (is_vm_hugetlb_page(vma) && !align_hugetlb(vrm)) {
res = -EINVAL;
goto out;
}
vrm_set_delta(vrm);
vrm->remap_type = vrm_remap_type(vrm);
/* Actually execute mremap. */
res = vrm_implies_new_addr(vrm) ? mremap_to(vrm) : mremap_at(vrm);