Correct a boundary case error in the management of a page's dirty bits by
shm_dotruncate() and vnode_pager_setsize(). Specifically, if the length of a shared memory object or a file is truncated such that the length modulo the page size is between 1 and 511, then all of the page's dirty bits were cleared. Now, a dirty bit is cleared only if the corresponding block is truncated in its entirety.
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parent
045e970615
commit
3c33df624c
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=193303
@ -274,7 +274,7 @@ shm_dotruncate(struct shmfd *shmfd, off_t length)
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/*
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* If the last page is partially mapped, then zero out
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* the garbage at the end of the page. See comments
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* in vnode_page_setsize() for more details.
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* in vnode_pager_setsize() for more details.
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*
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* XXXJHB: This handles in memory pages, but what about
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* a page swapped out to disk?
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@ -286,10 +286,23 @@ shm_dotruncate(struct shmfd *shmfd, off_t length)
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int size = PAGE_SIZE - base;
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pmap_zero_page_area(m, base, size);
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/*
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* Update the valid bits to reflect the blocks that
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* have been zeroed. Some of these valid bits may
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* have already been set.
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*/
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vm_page_set_valid(m, base, size);
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/*
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* Round "base" to the next block boundary so that the
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* dirty bit for a partially zeroed block is not
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* cleared.
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*/
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base = roundup2(base, DEV_BSIZE);
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vm_page_lock_queues();
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vm_page_set_validclean(m, base, size);
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if (m->dirty != 0)
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m->dirty = VM_PAGE_BITS_ALL;
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vm_page_clear_dirty(m, base, PAGE_SIZE - base);
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vm_page_unlock_queues();
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} else if ((length & PAGE_MASK) &&
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__predict_false(object->cache != NULL)) {
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@ -403,22 +403,28 @@ vnode_pager_setsize(vp, nsize)
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pmap_zero_page_area(m, base, size);
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/*
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* Clear out partial-page dirty bits. This
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* has the side effect of setting the valid
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* bits, but that is ok. There are a bunch
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* of places in the VM system where we expected
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* m->dirty == VM_PAGE_BITS_ALL. The file EOF
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* case is one of them. If the page is still
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* partially dirty, make it fully dirty.
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* Update the valid bits to reflect the blocks that
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* have been zeroed. Some of these valid bits may
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* have already been set.
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*/
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vm_page_set_valid(m, base, size);
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/*
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* Round "base" to the next block boundary so that the
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* dirty bit for a partially zeroed block is not
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* cleared.
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*/
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base = roundup2(base, DEV_BSIZE);
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/*
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* Clear out partial-page dirty bits.
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*
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* note that we do not clear out the valid
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* bits. This would prevent bogus_page
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* replacement from working properly.
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*/
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vm_page_lock_queues();
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vm_page_set_validclean(m, base, size);
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if (m->dirty != 0)
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m->dirty = VM_PAGE_BITS_ALL;
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vm_page_clear_dirty(m, base, PAGE_SIZE - base);
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vm_page_unlock_queues();
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} else if ((nsize & PAGE_MASK) &&
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__predict_false(object->cache != NULL)) {
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