iov_iter: first_{iovec,bvec}_segment() - simplify a bit

We return length + offset in page via *size. Don't bother - the caller
can do that arithmetics just as well; just report the length to it.

S

iov_iter: first_{iovec,bvec}_segment() - simplify a bit

We return length + offset in page via *size. Don't bother - the caller
can do that arithmetics just as well; just report the length to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

iov_iter: lift dealing with maxpages out of first_{iovec,bvec}_segment()

caller can do that just as easily

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

iov_iter_get_pages{,_alloc}(): cap the maxsize with MAX_RW_COUNT

All callers can and should handle iov_iter_get_pages() returning
fewer pages than requested. All in-kernel ones do. And it makes
th

iov_iter_get_pages{,_alloc}(): cap the maxsize with MAX_RW_COUNT

All callers can and should handle iov_iter_get_pages() returning
fewer pages than requested. All in-kernel ones do. And it makes
the arithmetical overflow analysis much simpler...

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

iov_iter_bvec_advance(): don't bother with bvec_iter

do what we do for iovec/kvec; that ends up generating better code,
AFAICS.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian

iov_iter_bvec_advance(): don't bother with bvec_iter

do what we do for iovec/kvec; that ends up generating better code,
AFAICS.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

fix short copy handling in copy_mc_pipe_to_iter()

Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short copy. In that case we need to trim the unused
buffers, as wel

fix short copy handling in copy_mc_pipe_to_iter()

Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short copy. In that case we need to trim the unused
buffers, as well as the length of partially filled one - it's not
enough to set ->head, ->iov_offset and ->count to reflect how
much had we copied. Not hard to fix, fortunately...

I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h,
rather than iov_iter.c - it has nothing to do with iov_iter and
having it will allow us to avoid an ugly kludge in fs/splice.c.
We could put it into lib/iov_iter.c for now and move it later,
but I don't see the point going that way...

Cc: stable@kernel.org # 4.19+
Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()"
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

copy_page_{to,from}_iter(): switch iovec variants to generic

we can do copyin/copyout under kmap_local_page(); it shouldn't overflow
the kmap stack - the maximal footprint increase only by one here.

copy_page_{to,from}_iter(): switch iovec variants to generic

we can do copyin/copyout under kmap_local_page(); it shouldn't overflow
the kmap stack - the maximal footprint increase only by one here.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

iov: introduce iov_iter_aligned

The existing iov_iter_alignment() function returns the logical OR of
address and length. For cases where address and length need to be
considered separately, introduc

iov: introduce iov_iter_aligned

The existing iov_iter_alignment() function returns the logical OR of
address and length. For cases where address and length need to be
considered separately, introduce a helper function that a caller can
specificy length and address masks that indicate if the iov is
unaligned.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220610195830.3574005-9-kbusch@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

show more ...

iov_iter: fix build issue due to possible type mis-match

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced a problem on some 32-bit architectures (at least arm, xtens

iov_iter: fix build issue due to possible type mis-match

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced a problem on some 32-bit architectures (at least arm, xtensa,
csky,sparc and mips), that have a 'size_t' that is 'unsigned int'.

The reason is that we now do

min(nr * PAGE_SIZE - offset, maxsize);

where 'nr' and 'offset' and both 'unsigned int', and PAGE_SIZE is
'unsigned long'. As a result, the normal C type rules means that the
first argument to 'min()' ends up being 'unsigned long'.

In contrast, 'maxsize' is of type 'size_t'.

Now, 'size_t' and 'unsigned long' are always the same physical type in
the kernel, so you'd think this doesn't matter, and from an actual
arithmetic standpoint it doesn't.

But on 32-bit architectures 'size_t' is commonly 'unsigned int', even if
it could also be 'unsigned long'. In that situation, both are unsigned
32-bit types, but they are not the *same* type.

And as a result 'min()' will complain about the distinct types (ignore
the "pointer types" part of the error message: that's an artifact of the
way we have made 'min()' check types for being the same):

lib/iov_iter.c: In function 'iter_xarray_get_pages':
include/linux/minmax.h:20:35: error: comparison of distinct pointer types lacks a cast [-Werror]
20 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
| ^~
lib/iov_iter.c:1464:16: note: in expansion of macro 'min'
1464 | return min(nr * PAGE_SIZE - offset, maxsize);
| ^~~

This was not visible on 64-bit architectures (where we always define
'size_t' to be 'unsigned long').

Force these cases to use 'min_t(size_t, x, y)' to make the type explicit
and avoid the issue.

[ Nit-picky note: technically 'size_t' doesn't have to match 'unsigned
long' arithmetically. We've certainly historically seen environments
with 16-bit address spaces and 32-bit 'unsigned long'.

Similarly, even in 64-bit modern environments, 'size_t' could be its
own type distinct from 'unsigned long', even if it were arithmetically
identical.

So the above type commentary is only really descriptive of the kernel
environment, not some kind of universal truth for the kinds of wild
and crazy situations that are allowed by the C standard ]

Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lore.kernel.org/all/YqRyL2sIqQNDfky2@debian/
Cc: Jeff Layton <jlayton@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work under some circumstances, such as when it's been asked to
ext

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work under some circumstances, such as when it's been asked to
extract a partial single page. Various terms of the equation cancel out
and you end up with actual == offset. The same issue exists in
iter_xarray_get_pages_alloc().

Fix these to just use min() to select the lesser amount from between the
amount of page content transcribed into the buffer, minus the offset, and
the size limit specified.

This doesn't appear to have caused a problem yet upstream because network
filesystems aren't getting the pages from an xarray iterator, but rather
passing it directly to the socket, which just iterates over it. Cachefiles
*does* do DIO from one to/from ext4/xfs/btrfs/etc. but it always asks for
whole pages to be written or read.

Fixes: 7ff5062079ef ("iov_iter: Add ITER_XARRAY")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Mike Marshall <hubcap@omnibond.com>
cc: Gao Xiang <xiang@kernel.org>
cc: linux-afs@lists.infradead.org
cc: v9fs-developer@lists.sourceforge.net
cc: devel@lists.orangefs.org
cc: linux-erofs@lists.ozlabs.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

lib/iov_iter: initialize "flags" in new pipe_buffer

The functions copy_page_to_iter_pipe() and push_pipe() can both
allocate a new pipe_buffer, but the "flags" member initializer is
missing.

Fixes:

lib/iov_iter: initialize "flags" in new pipe_buffer

The functions copy_page_to_iter_pipe() and push_pipe() can both
allocate a new pipe_buffer, but the "flags" member initializer is
missing.

Fixes: 241699cd72a8 ("new iov_iter flavour: pipe-backed")
To: Alexander Viro <viro@zeniv.linux.org.uk>
To: linux-fsdevel@vger.kernel.org
To: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

iov_iter: Convert iter_xarray to use folios

Take advantage of how kmap_local_folio() works to simplify the loop.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph

iov_iter: Convert iter_xarray to use folios

Take advantage of how kmap_local_folio() works to simplify the loop.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

show more ...

iov_iter: Introduce nofault flag to disable page faults

Introduce a new nofault flag to indicate to iov_iter_get_pages not to
fault in user pages.

This is implemented by passing the FOLL_NOFAULT fl

iov_iter: Introduce nofault flag to disable page faults

Introduce a new nofault flag to indicate to iov_iter_get_pages not to
fault in user pages.

This is implemented by passing the FOLL_NOFAULT flag to get_user_pages,
which causes get_user_pages to fail when it would otherwise fault in a
page. We'll use the ->nofault flag to prevent iomap_dio_rw from faulting
in pages when page faults are not allowed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

show more ...

iov_iter: Introduce fault_in_iov_iter_writeable

Introduce a new fault_in_iov_iter_writeable helper for safely faulting
in an iterator for writing. Uses get_user_pages() to fault in the pages
withou

iov_iter: Introduce fault_in_iov_iter_writeable

Introduce a new fault_in_iov_iter_writeable helper for safely faulting
in an iterator for writing. Uses get_user_pages() to fault in the pages
without actually writing to them, which would be destructive.

We'll use fault_in_iov_iter_writeable in gfs2 once we've determined that
the iterator passed to .read_iter isn't in memory.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

show more ...

iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable

Turn iov_iter_fault_in_readable into a function that returns the number
of bytes not faulted in, similar to copy_to_user, in

iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable

Turn iov_iter_fault_in_readable into a function that returns the number
of bytes not faulted in, similar to copy_to_user, instead of returning a
non-zero value when any of the requested pages couldn't be faulted in.
This supports the existing users that require all pages to be faulted in
as well as new users that are happy if any pages can be faulted in.

Rename iov_iter_fault_in_readable to fault_in_iov_iter_readable to make
sure this change doesn't silently break things.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

show more ...

gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

Turn fault_in_pages_{readable,writeable} into versions that return the
number of bytes not faulted in, similar to cop

gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

Turn fault_in_pages_{readable,writeable} into versions that return the
number of bytes not faulted in, similar to copy_to_user, instead of
returning a non-zero value when any of the requested pages couldn't be
faulted in. This supports the existing users that require all pages to
be faulted in as well as new users that are happy if any pages can be
faulted in.

Rename the functions to fault_in_{readable,writeable} to make sure
this change doesn't silently break things.

Neither of these functions is entirely trivial and it doesn't seem
useful to inline them, so move them to mm/gup.c.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

show more ...

iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value

Both iov_iter_get_pages and iov_iter_get_pages_alloc return the number
of bytes of the iovec they could get the pages for. When the

iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value

Both iov_iter_get_pages and iov_iter_get_pages_alloc return the number
of bytes of the iovec they could get the pages for. When they cannot
get any pages, they're supposed to return 0, but when the start of the
iovec isn't page aligned, the calculation goes wrong and they return a
negative value. Fix both functions.

In addition, change iov_iter_get_pages_alloc to return NULL in that case
to prevent resource leaks.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

show more ...

fix short copy handling in copy_mc_pipe_to_iter()

commit c3497fd009ef2c59eea60d21c3ac22de3585ed7d upstream.

Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short cop

fix short copy handling in copy_mc_pipe_to_iter()

commit c3497fd009ef2c59eea60d21c3ac22de3585ed7d upstream.

Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short copy. In that case we need to trim the unused
buffers, as well as the length of partially filled one - it's not
enough to set ->head, ->iov_offset and ->count to reflect how
much had we copied. Not hard to fix, fortunately...

I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h,
rather than iov_iter.c - it has nothing to do with iov_iter and
having it will allow us to avoid an ugly kludge in fs/splice.c.
We could put it into lib/iov_iter.c for now and move it later,
but I don't see the point going that way...

Cc: stable@kernel.org # 4.19+
Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()"
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

iov_iter: fix build issue due to possible type mis-match

commit 1c27f1fc1549f0e470429f5497a76ad28a37f21a upstream.

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced

iov_iter: fix build issue due to possible type mis-match

commit 1c27f1fc1549f0e470429f5497a76ad28a37f21a upstream.

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced a problem on some 32-bit architectures (at least arm, xtensa,
csky,sparc and mips), that have a 'size_t' that is 'unsigned int'.

The reason is that we now do

min(nr * PAGE_SIZE - offset, maxsize);

where 'nr' and 'offset' and both 'unsigned int', and PAGE_SIZE is
'unsigned long'. As a result, the normal C type rules means that the
first argument to 'min()' ends up being 'unsigned long'.

In contrast, 'maxsize' is of type 'size_t'.

Now, 'size_t' and 'unsigned long' are always the same physical type in
the kernel, so you'd think this doesn't matter, and from an actual
arithmetic standpoint it doesn't.

But on 32-bit architectures 'size_t' is commonly 'unsigned int', even if
it could also be 'unsigned long'. In that situation, both are unsigned
32-bit types, but they are not the *same* type.

And as a result 'min()' will complain about the distinct types (ignore
the "pointer types" part of the error message: that's an artifact of the
way we have made 'min()' check types for being the same):

lib/iov_iter.c: In function 'iter_xarray_get_pages':
include/linux/minmax.h:20:35: error: comparison of distinct pointer types lacks a cast [-Werror]
20 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
| ^~
lib/iov_iter.c:1464:16: note: in expansion of macro 'min'
1464 | return min(nr * PAGE_SIZE - offset, maxsize);
| ^~~

This was not visible on 64-bit architectures (where we always define
'size_t' to be 'unsigned long').

Force these cases to use 'min_t(size_t, x, y)' to make the type explicit
and avoid the issue.

[ Nit-picky note: technically 'size_t' doesn't have to match 'unsigned
long' arithmetically. We've certainly historically seen environments
with 16-bit address spaces and 32-bit 'unsigned long'.

Similarly, even in 64-bit modern environments, 'size_t' could be its
own type distinct from 'unsigned long', even if it were arithmetically
identical.

So the above type commentary is only really descriptive of the kernel
environment, not some kind of universal truth for the kinds of wild
and crazy situations that are allowed by the C standard ]

Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lore.kernel.org/all/YqRyL2sIqQNDfky2@debian/
Cc: Jeff Layton <jlayton@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

[ Upstream commit 6c77676645ad42993e0a8bdb8dafa517851a352a ]

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

[ Upstream commit 6c77676645ad42993e0a8bdb8dafa517851a352a ]

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work under some circumstances, such as when it's been asked to
extract a partial single page. Various terms of the equation cancel out
and you end up with actual == offset. The same issue exists in
iter_xarray_get_pages_alloc().

Fix these to just use min() to select the lesser amount from between the
amount of page content transcribed into the buffer, minus the offset, and
the size limit specified.

This doesn't appear to have caused a problem yet upstream because network
filesystems aren't getting the pages from an xarray iterator, but rather
passing it directly to the socket, which just iterates over it. Cachefiles
*does* do DIO from one to/from ext4/xfs/btrfs/etc. but it always asks for
whole pages to be written or read.

Fixes: 7ff5062079ef ("iov_iter: Add ITER_XARRAY")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Mike Marshall <hubcap@omnibond.com>
cc: Gao Xiang <xiang@kernel.org>
cc: linux-afs@lists.infradead.org
cc: v9fs-developer@lists.sourceforge.net
cc: devel@lists.orangefs.org
cc: linux-erofs@lists.ozlabs.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

iov_iter: fix build issue due to possible type mis-match

commit 1c27f1fc1549f0e470429f5497a76ad28a37f21a upstream.

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced

iov_iter: fix build issue due to possible type mis-match

commit 1c27f1fc1549f0e470429f5497a76ad28a37f21a upstream.

Commit 6c77676645ad ("iov_iter: Fix iter_xarray_get_pages{,_alloc}()")
introduced a problem on some 32-bit architectures (at least arm, xtensa,
csky,sparc and mips), that have a 'size_t' that is 'unsigned int'.

The reason is that we now do

min(nr * PAGE_SIZE - offset, maxsize);

where 'nr' and 'offset' and both 'unsigned int', and PAGE_SIZE is
'unsigned long'. As a result, the normal C type rules means that the
first argument to 'min()' ends up being 'unsigned long'.

In contrast, 'maxsize' is of type 'size_t'.

Now, 'size_t' and 'unsigned long' are always the same physical type in
the kernel, so you'd think this doesn't matter, and from an actual
arithmetic standpoint it doesn't.

But on 32-bit architectures 'size_t' is commonly 'unsigned int', even if
it could also be 'unsigned long'. In that situation, both are unsigned
32-bit types, but they are not the *same* type.

And as a result 'min()' will complain about the distinct types (ignore
the "pointer types" part of the error message: that's an artifact of the
way we have made 'min()' check types for being the same):

lib/iov_iter.c: In function 'iter_xarray_get_pages':
include/linux/minmax.h:20:35: error: comparison of distinct pointer types lacks a cast [-Werror]
20 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
| ^~
lib/iov_iter.c:1464:16: note: in expansion of macro 'min'
1464 | return min(nr * PAGE_SIZE - offset, maxsize);
| ^~~

This was not visible on 64-bit architectures (where we always define
'size_t' to be 'unsigned long').

Force these cases to use 'min_t(size_t, x, y)' to make the type explicit
and avoid the issue.

[ Nit-picky note: technically 'size_t' doesn't have to match 'unsigned
long' arithmetically. We've certainly historically seen environments
with 16-bit address spaces and 32-bit 'unsigned long'.

Similarly, even in 64-bit modern environments, 'size_t' could be its
own type distinct from 'unsigned long', even if it were arithmetically
identical.

So the above type commentary is only really descriptive of the kernel
environment, not some kind of universal truth for the kinds of wild
and crazy situations that are allowed by the C standard ]

Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lore.kernel.org/all/YqRyL2sIqQNDfky2@debian/
Cc: Jeff Layton <jlayton@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

[ Upstream commit 6c77676645ad42993e0a8bdb8dafa517851a352a ]

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work

iov_iter: Fix iter_xarray_get_pages{,_alloc}()

[ Upstream commit 6c77676645ad42993e0a8bdb8dafa517851a352a ]

The maths at the end of iter_xarray_get_pages() to calculate the actual
size doesn't work under some circumstances, such as when it's been asked to
extract a partial single page. Various terms of the equation cancel out
and you end up with actual == offset. The same issue exists in
iter_xarray_get_pages_alloc().

Fix these to just use min() to select the lesser amount from between the
amount of page content transcribed into the buffer, minus the offset, and
the size limit specified.

This doesn't appear to have caused a problem yet upstream because network
filesystems aren't getting the pages from an xarray iterator, but rather
passing it directly to the socket, which just iterates over it. Cachefiles
*does* do DIO from one to/from ext4/xfs/btrfs/etc. but it always asks for
whole pages to be written or read.

Fixes: 7ff5062079ef ("iov_iter: Add ITER_XARRAY")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Mike Marshall <hubcap@omnibond.com>
cc: Gao Xiang <xiang@kernel.org>
cc: linux-afs@lists.infradead.org
cc: v9fs-developer@lists.sourceforge.net
cc: devel@lists.orangefs.org
cc: linux-erofs@lists.ozlabs.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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iov_iter: Introduce nofault flag to disable page faults

commit 3337ab08d08b1a375f88471d9c8b1cac968cb054 upstream

Introduce a new nofault flag to indicate to iov_iter_get_pages not to
fault in user

iov_iter: Introduce nofault flag to disable page faults

commit 3337ab08d08b1a375f88471d9c8b1cac968cb054 upstream

Introduce a new nofault flag to indicate to iov_iter_get_pages not to
fault in user pages.

This is implemented by passing the FOLL_NOFAULT flag to get_user_pages,
which causes get_user_pages to fail when it would otherwise fault in a
page. We'll use the ->nofault flag to prevent iomap_dio_rw from faulting
in pages when page faults are not allowed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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iov_iter: Introduce fault_in_iov_iter_writeable

commit cdd591fc86e38ad3899196066219fbbd845f3162 upstream

Introduce a new fault_in_iov_iter_writeable helper for safely faulting
in an iterator for wr

iov_iter: Introduce fault_in_iov_iter_writeable

commit cdd591fc86e38ad3899196066219fbbd845f3162 upstream

Introduce a new fault_in_iov_iter_writeable helper for safely faulting
in an iterator for writing. Uses get_user_pages() to fault in the pages
without actually writing to them, which would be destructive.

We'll use fault_in_iov_iter_writeable in gfs2 once we've determined that
the iterator passed to .read_iter isn't in memory.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable

commit a6294593e8a1290091d0b078d5d33da5e0cd3dfe upstream

Turn iov_iter_fault_in_readable into a function that returns the n

iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable

commit a6294593e8a1290091d0b078d5d33da5e0cd3dfe upstream

Turn iov_iter_fault_in_readable into a function that returns the number
of bytes not faulted in, similar to copy_to_user, instead of returning a
non-zero value when any of the requested pages couldn't be faulted in.
This supports the existing users that require all pages to be faulted in
as well as new users that are happy if any pages can be faulted in.

Rename iov_iter_fault_in_readable to fault_in_iov_iter_readable to make
sure this change doesn't silently break things.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

commit bb523b406c849eef8f265a07cd7f320f1f177743 upstream

Turn fault_in_pages_{readable,writeable} into versions that

gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

commit bb523b406c849eef8f265a07cd7f320f1f177743 upstream

Turn fault_in_pages_{readable,writeable} into versions that return the
number of bytes not faulted in, similar to copy_to_user, instead of
returning a non-zero value when any of the requested pages couldn't be
faulted in. This supports the existing users that require all pages to
be faulted in as well as new users that are happy if any pages can be
faulted in.

Rename the functions to fault_in_{readable,writeable} to make sure
this change doesn't silently break things.

Neither of these functions is entirely trivial and it doesn't seem
useful to inline them, so move them to mm/gup.c.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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