Use a folio throughout __buffer_migrate_folio(), add kernel-doc for
buffer_migrate_folio() and buffer_migrate_folio_norefs(), move their
declarations to buffer.h and switch all filesystems that have wired
them up.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Use a folio throughout this function.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Use a folio throughout.  migrate_page() will be converted to
migrate_folio() later.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Provide a folio-based replacement for aops->migratepage.  Update the
documentation to document migrate_folio instead of migratepage.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

These drivers are rather uncomfortably hammered into the
address_space_operations hole.  They aren't filesystems and don't behave
like filesystems.  They just need their own movable_operations structure,
which we can point to directly from page->mapping.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

The isolate_page operation is never called for filesystems, only
for device drivers which call SetPageMovable.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>

Remove a call to read_mapping_page().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Use folio_put_refs() to perform only one atomic operation instead of two.
The other changes are straightforward conversions from page APIs to
their folio equivalents.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Use the folio API throughout.  There are a few places where we convert
back to a page to call into the rest of the filesystem, so folio usage
needs to be pushed down to those functions later.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Reorganise the file to remove the forward declaration.
Use folios throughout vxfs_immed_read_folio().
Use memcpy_to_page() instead of an open-coded kmap()/kunmap().
Remove flush_dcache_page() as this is embedded in memcpy_to_page().
Use folio_pos() instead of opencoding it.
Handle multi-page folios.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

This is a straightforward conversion from the page APIs to the folio
APIs.  Symlinks are not allowed to be larger than PAGE_SIZE, so there
is little work to do here.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

This is a straightforward conversion from the page APIs to the folio
APIs.  Symlinks are not allowed to be larger than PAGE_SIZE, so there
is little work to do here.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

This relatively straightforward converion saves a call to compound_head()
hidden inside put_page().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

The bare use of '9' confuses some people.  We also don't need this cast,
since the compiler does exactly that cast for us.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Set p->v to NULL if we try to read beyond the end of the disk, just like
we do if we get an error returned from trying to read the disk.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

That rather complicated expression is just trying to find the offset
of this sector within a page, and there are easier ways to express that.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Since commit 67f9fd91, the code to wait for the read to complete has
been dead.  That commit wrongly stated that the read was synchronous
already; this seems to have been a confusion about which ->readpage
operation was being called.  Instead of reintroducing an asynchronous
version of read_mapping_page(), call the readahead code directly to
submit all reads first before waiting for them in read_mapping_page().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Remove the open-coding of filemap_fdatawait_range().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If a page can't be written back, we need to call mapping_set_error(),
not clear the page's Uptodate flag.  Also remove the clearing of PageError
on success; that flag is used for read errors, not write errors.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Since we actually know what error happened, we can report it instead
of having the generic code return -EIO for pages that were unlocked
without being marked uptodate.  Also remove a test of PageError since
we have the return value at this point.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

We can cache this information in a local variable instead of communicating
from one part of the function to another via folio flags.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

The pagecache handles readpage failing by itself; it doesn't want
filesystems to remove pages from under it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If a buffer is completed with an error, its uptodate flag will be clear,
so the page_uptodate variable will have been set to 0.  There's no
need to check PageError here.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

The page cache clears the error bit before calling ->read_folio(),
so this condition could never have been true.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Just because there has been a read error doesn't mean we should avoid
marking this part of the folio as uptodate.  Indeed, it may overwrite
the error part of the folio and let us mark the entire folio uptodate.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Pages returned from read_mapping_page() are always uptodate, so
this check is unnecessary.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

read_mapping_folio() returns an ERR_PTR if the folio is not
uptodate, so this check is simply dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not
a page with PageError set, or a page that is not Uptodate, so this is
dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this test is not needed.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this test is not needed.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() encounters an error, it returns an errno, not a
page with PageError set, so this is dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If read_mapping_page() sees a page with PageError set, it returns a
PTR_ERR().  Checking PageError again is simply dead code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Add information on the use of 'file', whether ->read_folio should be
synchronous, and steer new callers towards calling read_mapping_folio()
instead of calling ->read_folio directly.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>