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folio: Add a function to get the host inode for a folio

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Add a convenience function, folio_inode() that will get the host inode from
a folio's mapping.

Changes:
 ver #3:
  - Fix mistake in function description[2].
 ver #2:
  - Fix contradiction between doc and implementation by disallowing use
    with swap caches[1].

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: Dominique Martinet <asmadeus@codewreck.org>
Tested-by: kafs-testing@auristor.com
Link: https://lore.kernel.org/r/YST8OcVNy02Rivbm@casper.infradead.org/ [1]
Link: https://lore.kernel.org/r/YYKLkBwQdtn4ja+i@casper.infradead.org/ [2]
Link: https://lore.kernel.org/r/162880453171.3369675.3704943108660112470.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/162981151155.1901565.7010079316994382707.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/163005744370.2472992.18324470937328925723.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163584184628.4023316.9386282630968981869.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/163649325519.309189.15072332908703129455.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/163657850401.834781.1031963517399283294.stgit@warthog.procyon.org.uk/ # v5
This commit is contained in:
David Howells 2021-08-12 22:09:57 +01:00
parent a19672f6b9
commit 452c472e26
2 changed files with 15 additions and 1 deletions
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14
include/linux/pagemap.h
View File

@ -253,6 +253,20 @@ static inline struct address_space *page_mapping_file(struct page *page)
return folio_mapping(folio);
}
/**
* folio_inode - Get the host inode for this folio.
* @folio: The folio.
*
* For folios which are in the page cache, return the inode that this folio
* belongs to.
*
* Do not call this for folios which aren't in the page cache.
*/
static inline struct inode *folio_inode(struct folio *folio)
{
return folio->mapping->host;
}
static inline bool page_cache_add_speculative(struct page *page, int count)
{
VM_BUG_ON_PAGE(PageTail(page), page);

2
mm/page-writeback.c
View File

@ -2967,7 +2967,7 @@ EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);
*/
void folio_wait_stable(struct folio *folio)
{
if (folio->mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
if (folio_inode(folio)->i_sb->s_iflags & SB_I_STABLE_WRITES)
folio_wait_writeback(folio);
}
EXPORT_SYMBOL_GPL(folio_wait_stable);