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mm: Add set/end/wait functions for PG_private_2
Add three functions to manipulate PG_private_2: (*) set_page_private_2() - Set the flag and take an appropriate reference on the flagged page. (*) end_page_private_2() - Clear the flag, drop the reference and wake up any waiters, somewhat analogously with end_page_writeback(). (*) wait_on_page_private_2() - Wait for the flag to be cleared. Wrappers will need to be placed in the netfs lib header in the patch that adds that. [This implements a suggestion by Linus[1] to not mix the terminology of PG_private_2 and PG_fscache in the mm core function] Changes: v7: - Use compound_head() in all the functions to make them THP safe[6]. v5: - Add set and end functions, calling the end function end rather than unlock[3]. - Keep a ref on the page when PG_private_2 is set[4][5]. v4: - Remove extern from the declaration[2]. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Tested-by: Jeff Layton <jlayton@kernel.org> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Tested-By: Marc Dionne <marc.dionne@auristor.com> cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Christoph Hellwig <hch@lst.de> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/1330473.1612974547@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/CAHk-=wjgA-74ddehziVk=XAEMTKswPu1Yw4uaro1R3ibs27ztw@mail.gmail.com/ [1] Link: https://lore.kernel.org/r/20210216102659.GA27714@lst.de/ [2] Link: https://lore.kernel.org/r/161340387944.1303470.7944159520278177652.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539528910.286939.1252328699383291173.stgit@warthog.procyon.org.uk # v4 Link: https://lore.kernel.org/r/20210321105309.GG3420@casper.infradead.org [3] Link: https://lore.kernel.org/r/CAHk-=wh+2gbF7XEjYc=HV9w_2uVzVf7vs60BPz0gFA=+pUm3ww@mail.gmail.com/ [4] Link: https://lore.kernel.org/r/CAHk-=wjSGsRj7xwhSMQ6dAQiz53xA39pOG+XA_WeTgwBBu4uqg@mail.gmail.com/ [5] Link: https://lore.kernel.org/r/20210408145057.GN2531743@casper.infradead.org/ [6] Link: https://lore.kernel.org/r/161653788200.2770958.9517755716374927208.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789066013.6155.9816857201817288382.stgit@warthog.procyon.org.uk/ # v6
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73e10ded33
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@ -688,6 +688,26 @@ void wait_for_stable_page(struct page *page);
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void page_endio(struct page *page, bool is_write, int err);
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/**
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* set_page_private_2 - Set PG_private_2 on a page and take a ref
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* @page: The page.
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*
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* Set the PG_private_2 flag on a page and take the reference needed for the VM
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* to handle its lifetime correctly. This sets the flag and takes the
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* reference unconditionally, so care must be taken not to set the flag again
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* if it's already set.
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*/
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static inline void set_page_private_2(struct page *page)
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{
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page = compound_head(page);
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get_page(page);
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SetPagePrivate2(page);
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}
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void end_page_private_2(struct page *page);
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void wait_on_page_private_2(struct page *page);
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int wait_on_page_private_2_killable(struct page *page);
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/*
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* Add an arbitrary waiter to a page's wait queue
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*/
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61
mm/filemap.c
61
mm/filemap.c
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@ -1432,6 +1432,67 @@ void unlock_page(struct page *page)
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}
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EXPORT_SYMBOL(unlock_page);
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/**
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* end_page_private_2 - Clear PG_private_2 and release any waiters
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* @page: The page
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*
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* Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
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* this. The page ref held for PG_private_2 being set is released.
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*
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* This is, for example, used when a netfs page is being written to a local
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* disk cache, thereby allowing writes to the cache for the same page to be
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* serialised.
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*/
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void end_page_private_2(struct page *page)
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{
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page = compound_head(page);
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VM_BUG_ON_PAGE(!PagePrivate2(page), page);
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clear_bit_unlock(PG_private_2, &page->flags);
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wake_up_page_bit(page, PG_private_2);
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put_page(page);
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}
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EXPORT_SYMBOL(end_page_private_2);
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/**
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* wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
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* @page: The page to wait on
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*
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* Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
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*/
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void wait_on_page_private_2(struct page *page)
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{
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page = compound_head(page);
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while (PagePrivate2(page))
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wait_on_page_bit(page, PG_private_2);
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}
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EXPORT_SYMBOL(wait_on_page_private_2);
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/**
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* wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
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* @page: The page to wait on
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*
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* Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
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* fatal signal is received by the calling task.
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*
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* Return:
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* - 0 if successful.
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* - -EINTR if a fatal signal was encountered.
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*/
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int wait_on_page_private_2_killable(struct page *page)
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{
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int ret = 0;
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page = compound_head(page);
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while (PagePrivate2(page)) {
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ret = wait_on_page_bit_killable(page, PG_private_2);
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if (ret < 0)
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break;
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}
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return ret;
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}
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EXPORT_SYMBOL(wait_on_page_private_2_killable);
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/**
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* end_page_writeback - end writeback against a page
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* @page: the page
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