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xfs: use iomap_dio_rw
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Straight switch over to using iomap for direct I/O - we already have the
non-COW dio path in write_begin for DAX and files with extent size hints,
so nothing to add there.  The COW path is ported over from the old
get_blocks version and a bit of a mess, but I have some work in progress
to make it look more like the buffered I/O COW path.

This gets rid of xfs_get_blocks_direct and the last caller of
xfs_get_blocks with the create flag set, so all that code can be removed.

Last but not least I've removed a comment in xfs_filemap_fault that
refers to xfs_get_blocks entirely instead of updating it - while the
reference is correct, the whole DAX fault path looks different than
the non-DAX one, so it seems rather pointless.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Christoph Hellwig authored and Dave Chinner committed Nov 30, 2016
1 parent ff6a929 commit acdda3a
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Showing 4 changed files with 110 additions and 386 deletions.
291 changes: 8 additions & 283 deletions fs/xfs/xfs_aops.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,6 @@
#include <linux/pagevec.h>
#include <linux/writeback.h>

/* flags for direct write completions */
#define XFS_DIO_FLAG_UNWRITTEN (1 << 0)
#define XFS_DIO_FLAG_APPEND (1 << 1)
#define XFS_DIO_FLAG_COW (1 << 2)

/*
* structure owned by writepages passed to individual writepage calls
*/
Expand Down Expand Up @@ -1175,45 +1170,6 @@ xfs_vm_releasepage(
return try_to_free_buffers(page);
}

/*
* When we map a DIO buffer, we may need to pass flags to
* xfs_end_io_direct_write to tell it what kind of write IO we are doing.
*
* Note that for DIO, an IO to the highest supported file block offset (i.e.
* 2^63 - 1FSB bytes) will result in the offset + count overflowing a signed 64
* bit variable. Hence if we see this overflow, we have to assume that the IO is
* extending the file size. We won't know for sure until IO completion is run
* and the actual max write offset is communicated to the IO completion
* routine.
*/
static void
xfs_map_direct(
struct inode *inode,
struct buffer_head *bh_result,
struct xfs_bmbt_irec *imap,
xfs_off_t offset,
bool is_cow)
{
uintptr_t *flags = (uintptr_t *)&bh_result->b_private;
xfs_off_t size = bh_result->b_size;

trace_xfs_get_blocks_map_direct(XFS_I(inode), offset, size,
ISUNWRITTEN(imap) ? XFS_IO_UNWRITTEN : is_cow ? XFS_IO_COW :
XFS_IO_OVERWRITE, imap);

if (ISUNWRITTEN(imap)) {
*flags |= XFS_DIO_FLAG_UNWRITTEN;
set_buffer_defer_completion(bh_result);
} else if (is_cow) {
*flags |= XFS_DIO_FLAG_COW;
set_buffer_defer_completion(bh_result);
}
if (offset + size > i_size_read(inode) || offset + size < 0) {
*flags |= XFS_DIO_FLAG_APPEND;
set_buffer_defer_completion(bh_result);
}
}

/*
* If this is O_DIRECT or the mpage code calling tell them how large the mapping
* is, so that we can avoid repeated get_blocks calls.
Expand Down Expand Up @@ -1254,51 +1210,12 @@ xfs_map_trim_size(
bh_result->b_size = mapping_size;
}

/* Bounce unaligned directio writes to the page cache. */
static int
xfs_bounce_unaligned_dio_write(
struct xfs_inode *ip,
xfs_fileoff_t offset_fsb,
struct xfs_bmbt_irec *imap)
{
struct xfs_bmbt_irec irec;
xfs_fileoff_t delta;
bool shared;
bool x;
int error;

irec = *imap;
if (offset_fsb > irec.br_startoff) {
delta = offset_fsb - irec.br_startoff;
irec.br_blockcount -= delta;
irec.br_startblock += delta;
irec.br_startoff = offset_fsb;
}
error = xfs_reflink_trim_around_shared(ip, &irec, &shared, &x);
if (error)
return error;

/*
* We're here because we're trying to do a directio write to a
* region that isn't aligned to a filesystem block. If any part
* of the extent is shared, fall back to buffered mode to handle
* the RMW. This is done by returning -EREMCHG ("remote addr
* changed"), which is caught further up the call stack.
*/
if (shared) {
trace_xfs_reflink_bounce_dio_write(ip, imap);
return -EREMCHG;
}
return 0;
}

STATIC int
__xfs_get_blocks(
xfs_get_blocks(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create,
bool direct)
int create)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
Expand All @@ -1309,10 +1226,8 @@ __xfs_get_blocks(
int nimaps = 1;
xfs_off_t offset;
ssize_t size;
int new = 0;
bool is_cow = false;

BUG_ON(create && !direct);
BUG_ON(create);

if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
Expand All @@ -1321,7 +1236,7 @@ __xfs_get_blocks(
ASSERT(bh_result->b_size >= (1 << inode->i_blkbits));
size = bh_result->b_size;

if (!create && offset >= i_size_read(inode))
if (offset >= i_size_read(inode))
return 0;

/*
Expand All @@ -1336,73 +1251,12 @@ __xfs_get_blocks(
end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + size);
offset_fsb = XFS_B_TO_FSBT(mp, offset);

if (create && direct && xfs_is_reflink_inode(ip)) {
is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap);
ASSERT(!is_cow || !isnullstartblock(imap.br_startblock));
}

if (!is_cow) {
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
&imap, &nimaps, XFS_BMAPI_ENTIRE);
/*
* Truncate an overwrite extent if there's a pending CoW
* reservation before the end of this extent. This
* forces us to come back to get_blocks to take care of
* the CoW.
*/
if (create && direct && nimaps &&
imap.br_startblock != HOLESTARTBLOCK &&
imap.br_startblock != DELAYSTARTBLOCK &&
!ISUNWRITTEN(&imap))
xfs_reflink_trim_irec_to_next_cow(ip, offset_fsb,
&imap);
}
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
&imap, &nimaps, XFS_BMAPI_ENTIRE);
if (error)
goto out_unlock;

/*
* The only time we can ever safely find delalloc blocks on direct I/O
* is a dio write to post-eof speculative preallocation. All other
* scenarios are indicative of a problem or misuse (such as mixing
* direct and mapped I/O).
*
* The file may be unmapped by the time we get here so we cannot
* reliably fail the I/O based on mapping. Instead, fail the I/O if this
* is a read or a write within eof. Otherwise, carry on but warn as a
* precuation if the file happens to be mapped.
*/
if (direct && imap.br_startblock == DELAYSTARTBLOCK) {
if (!create || offset < i_size_read(VFS_I(ip))) {
WARN_ON_ONCE(1);
error = -EIO;
goto out_unlock;
}
WARN_ON_ONCE(mapping_mapped(VFS_I(ip)->i_mapping));
}

/* for DAX, we convert unwritten extents directly */
if (create &&
(!nimaps ||
(imap.br_startblock == HOLESTARTBLOCK ||
imap.br_startblock == DELAYSTARTBLOCK) ||
(IS_DAX(inode) && ISUNWRITTEN(&imap)))) {
/*
* xfs_iomap_write_direct() expects the shared lock. It
* is unlocked on return.
*/
if (lockmode == XFS_ILOCK_EXCL)
xfs_ilock_demote(ip, lockmode);

error = xfs_iomap_write_direct(ip, offset, size,
&imap, nimaps);
if (error)
return error;
new = 1;

trace_xfs_get_blocks_alloc(ip, offset, size,
ISUNWRITTEN(&imap) ? XFS_IO_UNWRITTEN
: XFS_IO_DELALLOC, &imap);
} else if (nimaps) {
if (nimaps) {
trace_xfs_get_blocks_found(ip, offset, size,
ISUNWRITTEN(&imap) ? XFS_IO_UNWRITTEN
: XFS_IO_OVERWRITE, &imap);
Expand All @@ -1412,12 +1266,6 @@ __xfs_get_blocks(
goto out_unlock;
}

if (IS_DAX(inode) && create) {
ASSERT(!ISUNWRITTEN(&imap));
/* zeroing is not needed at a higher layer */
new = 0;
}

/* trim mapping down to size requested */
xfs_map_trim_size(inode, iblock, bh_result, &imap, offset, size);

Expand All @@ -1427,144 +1275,21 @@ __xfs_get_blocks(
*/
if (imap.br_startblock != HOLESTARTBLOCK &&
imap.br_startblock != DELAYSTARTBLOCK &&
(create || !ISUNWRITTEN(&imap))) {
if (create && direct && !is_cow) {
error = xfs_bounce_unaligned_dio_write(ip, offset_fsb,
&imap);
if (error)
return error;
}

!ISUNWRITTEN(&imap))
xfs_map_buffer(inode, bh_result, &imap, offset);
if (ISUNWRITTEN(&imap))
set_buffer_unwritten(bh_result);
/* direct IO needs special help */
if (create)
xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
}

/*
* If this is a realtime file, data may be on a different device.
* to that pointed to from the buffer_head b_bdev currently.
*/
bh_result->b_bdev = xfs_find_bdev_for_inode(inode);

/*
* If we previously allocated a block out beyond eof and we are now
* coming back to use it then we will need to flag it as new even if it
* has a disk address.
*
* With sub-block writes into unwritten extents we also need to mark
* the buffer as new so that the unwritten parts of the buffer gets
* correctly zeroed.
*/
if (create &&
((!buffer_mapped(bh_result) && !buffer_uptodate(bh_result)) ||
(offset >= i_size_read(inode)) ||
(new || ISUNWRITTEN(&imap))))
set_buffer_new(bh_result);

return 0;

out_unlock:
xfs_iunlock(ip, lockmode);
return error;
}

int
xfs_get_blocks(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create)
{
return __xfs_get_blocks(inode, iblock, bh_result, create, false);
}

int
xfs_get_blocks_direct(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create)
{
return __xfs_get_blocks(inode, iblock, bh_result, create, true);
}

/*
* Complete a direct I/O write request.
*
* xfs_map_direct passes us some flags in the private data to tell us what to
* do. If no flags are set, then the write IO is an overwrite wholly within
* the existing allocated file size and so there is nothing for us to do.
*
* Note that in this case the completion can be called in interrupt context,
* whereas if we have flags set we will always be called in task context
* (i.e. from a workqueue).
*/
int
xfs_end_io_direct_write(
struct kiocb *iocb,
loff_t offset,
ssize_t size,
void *private)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct xfs_inode *ip = XFS_I(inode);
uintptr_t flags = (uintptr_t)private;
int error = 0;

trace_xfs_end_io_direct_write(ip, offset, size);

if (XFS_FORCED_SHUTDOWN(ip->i_mount))
return -EIO;

if (size <= 0)
return size;

/*
* The flags tell us whether we are doing unwritten extent conversions
* or an append transaction that updates the on-disk file size. These
* cases are the only cases where we should *potentially* be needing
* to update the VFS inode size.
*/
if (flags == 0) {
ASSERT(offset + size <= i_size_read(inode));
return 0;
}

/*
* We need to update the in-core inode size here so that we don't end up
* with the on-disk inode size being outside the in-core inode size. We
* have no other method of updating EOF for AIO, so always do it here
* if necessary.
*
* We need to lock the test/set EOF update as we can be racing with
* other IO completions here to update the EOF. Failing to serialise
* here can result in EOF moving backwards and Bad Things Happen when
* that occurs.
*/
spin_lock(&ip->i_flags_lock);
if (offset + size > i_size_read(inode))
i_size_write(inode, offset + size);
spin_unlock(&ip->i_flags_lock);

if (flags & XFS_DIO_FLAG_COW)
error = xfs_reflink_end_cow(ip, offset, size);
if (flags & XFS_DIO_FLAG_UNWRITTEN) {
trace_xfs_end_io_direct_write_unwritten(ip, offset, size);

error = xfs_iomap_write_unwritten(ip, offset, size);
}
if (flags & XFS_DIO_FLAG_APPEND) {
trace_xfs_end_io_direct_write_append(ip, offset, size);

error = xfs_setfilesize(ip, offset, size);
}

return error;
}

STATIC ssize_t
xfs_vm_direct_IO(
struct kiocb *iocb,
Expand Down
6 changes: 0 additions & 6 deletions fs/xfs/xfs_aops.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,12 +55,6 @@ struct xfs_ioend {

extern const struct address_space_operations xfs_address_space_operations;

int xfs_get_blocks(struct inode *inode, sector_t offset,
struct buffer_head *map_bh, int create);
int xfs_get_blocks_direct(struct inode *inode, sector_t offset,
struct buffer_head *map_bh, int create);
int xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
ssize_t size, void *private);
int xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);

extern void xfs_count_page_state(struct page *, int *, int *);
Expand Down
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