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ipc/shm: use VMA iterator instead of linked list 

JIRA: https://issues.redhat.com/browse/RHEL-27736

commit 01293a62bae2fa55c09cebf5a771eab7219171c3
Author: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date:   Tue Sep 6 19:48:58 2022 +0000

    ipc/shm: use VMA iterator instead of linked list

    The VMA iterator is faster than the linked llist, and it can be walked
    even when VMAs are being removed from the address space, so there's no
    need to keep track of 'next'.

    Link: https://lkml.kernel.org/r/20220906194824.2110408-46-Liam.Howlett@oracle.com
    Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    Tested-by: Yu Zhao <yuzhao@google.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: David Hildenbrand <david@redhat.com>
    Cc: David Howells <dhowells@redhat.com>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: SeongJae Park <sj@kernel.org>
    Cc: Sven Schnelle <svens@linux.ibm.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Will Deacon <will@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
This commit is contained in:
Chris von Recklinghausen 2024-04-01 11:19:51 -04:00
parent b0ae9352e7
commit 610f900b75
1 changed files with 10 additions and 11 deletions
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21
ipc/shm.c
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@ -1640,7 +1640,7 @@ long ksys_shmdt(char __user *shmaddr)
#ifdef CONFIG_MMU
loff_t size = 0;
struct file *file;
struct vm_area_struct *next;
VMA_ITERATOR(vmi, mm, addr);
#endif
if (addr & ~PAGE_MASK)
@ -1670,12 +1670,9 @@ long ksys_shmdt(char __user *shmaddr)
* match the usual checks anyway. So assume all vma's are
* above the starting address given.
*/
vma = find_vma(mm, addr);
#ifdef CONFIG_MMU
while (vma) {
next = vma->vm_next;
for_each_vma(vmi, vma) {
/*
* Check if the starting address would match, i.e. it's
* a fragment created by mprotect() and/or munmap(), or it
@ -1693,6 +1690,7 @@ long ksys_shmdt(char __user *shmaddr)
file = vma->vm_file;
size = i_size_read(file_inode(vma->vm_file));
do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
mas_pause(&vmi.mas);
/*
* We discovered the size of the shm segment, so
* break out of here and fall through to the next
@ -1700,10 +1698,9 @@ long ksys_shmdt(char __user *shmaddr)
* searching for matching vma's.
*/
retval = 0;
vma = next;
vma = vma_next(&vmi);
break;
}
vma = next;
}
/*
@ -1713,17 +1710,19 @@ long ksys_shmdt(char __user *shmaddr)
*/
size = PAGE_ALIGN(size);
while (vma && (loff_t)(vma->vm_end - addr) <= size) {
next = vma->vm_next;
/* finding a matching vma now does not alter retval */
if ((vma->vm_ops == &shm_vm_ops) &&
((vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) &&
(vma->vm_file == file))
(vma->vm_file == file)) {
do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
vma = next;
mas_pause(&vmi.mas);
}
vma = vma_next(&vmi);
}
#else /* CONFIG_MMU */
vma = vma_lookup(mm, addr);
/* under NOMMU conditions, the exact address to be destroyed must be
* given
*/