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e2f6ad4624
linux_dsm_epyc7002/fs/xfs/xfs_aops.c
Dave Chinner e2f6ad4624 xfs: make xfs_writepage_map extent map centric 
xfs_writepage_map() iterates over the bufferheads on a page to decide
what sort of IO to do and what actions to take.  However, when it comes
to reflink and deciding when it needs to execute a COW operation, we no
longer look at the bufferhead state but instead we ignore than and look
up internal state held in the COW fork extent list.

This means xfs_writepage_map() is somewhat confused. It does stuff, then
ignores it, then tries to handle the impedence mismatch by shovelling the
results inside the existing mapping code.  It works, but it's a bit of a
mess and it makes it hard to fix the cached map bug that the writepage
code currently has.

To unify the two different mechanisms, we first have to choose a direction.
That's already been set - we're de-emphasising bufferheads so they are no
longer a control structure as we need to do taht to allow for eventual
removal.  Hence we need to move away from looking at bufferhead state to
determine what operations we need to perform.

We can't completely get rid of bufferheads yet - they do contain some
state that is absolutely necessary, such as whether that part of the page
contains valid data or not (buffer_uptodate()).  Other state in the
bufferhead is redundant:

	BH_dirty - the page is dirty, so we can ignore this and just
		write it
	BH_delay - we have delalloc extent info in the DATA fork extent
		tree
	BH_unwritten - same as BH_delay
	BH_mapped - indicates we've already used it once for IO and it is
		mapped to a disk address. Needs to be ignored for COW
		blocks.

The BH_mapped flag is an interesting case - it's supposed to indicate that
it's already mapped to disk and so we can just use it "as is".  In theory,
we don't even have to do an extent lookup to find where to write it too,
but we have to do that anyway to determine we are actually writing over a
valid extent.  Hence it's not even serving the purpose of avoiding a an
extent lookup during writeback, and so we can pretty much ignore it.
Especially as we have to ignore it for COW operations...

Therefore, use the extent map as the source of information to tell us
what actions we need to take and what sort of IO we should perform.  The
first step is to have xfs_map_blocks() set the io type according to what
it looks up.  This means it can easily handle both normal overwrite and
COW cases.  The only thing we also need to add is the ability to return
hole mappings.

We need to return and cache hole mappings now for the case of multiple
blocks per page.  We no longer use the BH_mapped to indicate a block over
a hole, so we have to get that info from xfs_map_blocks().  We cache it so
that holes that span two pages don't need separate lookups.  This allows us
to avoid ever doing write IO over a hole, too.

Now that we have xfs_map_blocks() returning both a cached map and the type
of IO we need to perform, we can rewrite xfs_writepage_map() to drop all
the bufferhead control. It's also much simplified because it doesn't need
to explicitly handle COW operations.  Instead of iterating bufferheads, it
iterates blocks within the page and then looks up what per-block state is
required from the appropriate bufferhead.  It then validates the cached
map, and if it's not valid, we get a new map.  If we don't get a valid map
or it's over a hole, we skip the block.

At this point, we have to remap the bufferhead via xfs_map_at_offset().
As previously noted, we had to do this even if the buffer was already
mapped as the mapping would be stale for XFS_IO_DELALLOC, XFS_IO_UNWRITTEN
and XFS_IO_COW IO types.  With xfs_map_blocks() now controlling the type,
even XFS_IO_OVERWRITE types need remapping, as converted-but-not-yet-
written delalloc extents beyond EOF can be reported at XFS_IO_OVERWRITE.
Bufferheads that span such regions still need their BH_Delay flags cleared
and their block numbers calculated, so we now unconditionally map each
bufferhead before submission.

But wait! There's more - remember the old "treat unwritten extents as
holes on read" hack?  Yeah, that means we can have a dirty page with
unmapped, unwritten bufferheads that contain data!  What makes these so
special is that the unwritten "hole" bufferheads do not have a valid block
device pointer, so if we attempt to write them xfs_add_to_ioend() blows
up. So we make xfs_map_at_offset() do the "realtime or data device"
lookup from the inode and ignore what was or wasn't put into the
bufferhead when the buffer was instantiated.

The astute reader will have realised by now that this code treats
unwritten extents in multiple-blocks-per-page situations differently.
If we get any combination of unwritten blocks on a dirty page that contain
valid data in the page, we're going to convert them to real extents.  This
can actually be a win, because it means that pages with interleaving
unwritten and written blocks will get converted to a single written extent
with zeros replacing the interspersed unwritten blocks.  This is actually
good for reducing extent list and conversion overhead, and it means we
issue a contiguous IO instead of lots of little ones.  The downside is
that we use up a little extra IO bandwidth.  Neither of these seem like a
bad thing given that spinning disks are seek sensitive, and SSDs/pmem have
bandwidth to burn and the lower Io latency/CPU overhead of fewer, larger
IOs will result in better performance on them...

As a result of all this, the only state we actually care about from the
bufferhead is a single flag - BH_Uptodate. We still use the bufferhead to
pass some information to the bio via xfs_add_to_ioend(), but that is
trivial to separate and pass explicitly.  This means we really only need
1 bit of state per block per page from the buffered write path in the
writeback path.  Everything else we do with the bufferhead is purely to
make the buffered IO front end continue to work correctly. i.e we've
pretty much marginalised bufferheads in the writeback path completely.

Signed-off-By: Dave Chinner <dchinner@redhat.com>
[hch: forward port, refactor and split off bits into other commits]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-07-11 22:26:00 -07:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2005 Silicon Graphics, Inc.
* All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_alloc.h"
#include "xfs_error.h"
#include "xfs_iomap.h"
#include "xfs_trace.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
#include "xfs_reflink.h"
#include <linux/gfp.h>
#include <linux/mpage.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
/*
* structure owned by writepages passed to individual writepage calls
*/
struct xfs_writepage_ctx {
struct xfs_bmbt_irec imap;
bool imap_valid;
unsigned int io_type;
struct xfs_ioend *ioend;
sector_t last_block;
};
void
xfs_count_page_state(
struct page *page,
int *delalloc,
int *unwritten)
{
struct buffer_head *bh, *head;
*delalloc = *unwritten = 0;
bh = head = page_buffers(page);
do {
if (buffer_unwritten(bh))
(*unwritten) = 1;
else if (buffer_delay(bh))
(*delalloc) = 1;
} while ((bh = bh->b_this_page) != head);
}
struct block_device *
xfs_find_bdev_for_inode(
struct inode *inode)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
if (XFS_IS_REALTIME_INODE(ip))
return mp->m_rtdev_targp->bt_bdev;
else
return mp->m_ddev_targp->bt_bdev;
}
struct dax_device *
xfs_find_daxdev_for_inode(
struct inode *inode)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
if (XFS_IS_REALTIME_INODE(ip))
return mp->m_rtdev_targp->bt_daxdev;
else
return mp->m_ddev_targp->bt_daxdev;
}
/*
* We're now finished for good with this page. Update the page state via the
* associated buffer_heads, paying attention to the start and end offsets that
* we need to process on the page.
*
* Note that we open code the action in end_buffer_async_write here so that we
* only have to iterate over the buffers attached to the page once. This is not
* only more efficient, but also ensures that we only calls end_page_writeback
* at the end of the iteration, and thus avoids the pitfall of having the page
* and buffers potentially freed after every call to end_buffer_async_write.
*/
static void
xfs_finish_page_writeback(
struct inode *inode,
struct bio_vec *bvec,
int error)
{
struct buffer_head *head = page_buffers(bvec->bv_page), *bh = head;
bool busy = false;
unsigned int off = 0;
unsigned long flags;
ASSERT(bvec->bv_offset < PAGE_SIZE);
ASSERT((bvec->bv_offset & (i_blocksize(inode) - 1)) == 0);
ASSERT(bvec->bv_offset + bvec->bv_len <= PAGE_SIZE);
ASSERT((bvec->bv_len & (i_blocksize(inode) - 1)) == 0);
local_irq_save(flags);
bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
do {
if (off >= bvec->bv_offset &&
off < bvec->bv_offset + bvec->bv_len) {
ASSERT(buffer_async_write(bh));
ASSERT(bh->b_end_io == NULL);
if (error) {
mark_buffer_write_io_error(bh);
clear_buffer_uptodate(bh);
SetPageError(bvec->bv_page);
} else {
set_buffer_uptodate(bh);
}
clear_buffer_async_write(bh);
unlock_buffer(bh);
} else if (buffer_async_write(bh)) {
ASSERT(buffer_locked(bh));
busy = true;
}
off += bh->b_size;
} while ((bh = bh->b_this_page) != head);
bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
local_irq_restore(flags);
if (!busy)
end_page_writeback(bvec->bv_page);
}
/*
* We're now finished for good with this ioend structure. Update the page
* state, release holds on bios, and finally free up memory. Do not use the
* ioend after this.
*/
STATIC void
xfs_destroy_ioend(
struct xfs_ioend *ioend,
int error)
{
struct inode *inode = ioend->io_inode;
struct bio *bio = &ioend->io_inline_bio;
struct bio *last = ioend->io_bio, *next;
u64 start = bio->bi_iter.bi_sector;
bool quiet = bio_flagged(bio, BIO_QUIET);
for (bio = &ioend->io_inline_bio; bio; bio = next) {
struct bio_vec *bvec;
int i;
/*
* For the last bio, bi_private points to the ioend, so we
* need to explicitly end the iteration here.
*/
if (bio == last)
next = NULL;
else
next = bio->bi_private;
/* walk each page on bio, ending page IO on them */
bio_for_each_segment_all(bvec, bio, i)
xfs_finish_page_writeback(inode, bvec, error);
bio_put(bio);
}
if (unlikely(error && !quiet)) {
xfs_err_ratelimited(XFS_I(inode)->i_mount,
"writeback error on sector %llu", start);
}
}
/*
* Fast and loose check if this write could update the on-disk inode size.
*/
static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
{
return ioend->io_offset + ioend->io_size >
XFS_I(ioend->io_inode)->i_d.di_size;
}
STATIC int
xfs_setfilesize_trans_alloc(
struct xfs_ioend *ioend)
{
struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount;
struct xfs_trans *tp;
int error;
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0,
XFS_TRANS_NOFS, &tp);
if (error)
return error;
ioend->io_append_trans = tp;
/*
* We may pass freeze protection with a transaction. So tell lockdep
* we released it.
*/
__sb_writers_release(ioend->io_inode->i_sb, SB_FREEZE_FS);
/*
* We hand off the transaction to the completion thread now, so
* clear the flag here.
*/
current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
return 0;
}
/*
* Update on-disk file size now that data has been written to disk.
*/
STATIC int
__xfs_setfilesize(
struct xfs_inode *ip,
struct xfs_trans *tp,
xfs_off_t offset,
size_t size)
{
xfs_fsize_t isize;
xfs_ilock(ip, XFS_ILOCK_EXCL);
isize = xfs_new_eof(ip, offset + size);
if (!isize) {
xfs_iunlock(ip, XFS_ILOCK_EXCL);
xfs_trans_cancel(tp);
return 0;
}
trace_xfs_setfilesize(ip, offset, size);
ip->i_d.di_size = isize;
xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
return xfs_trans_commit(tp);
}
int
xfs_setfilesize(
struct xfs_inode *ip,
xfs_off_t offset,
size_t size)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_trans *tp;
int error;
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
if (error)
return error;
return __xfs_setfilesize(ip, tp, offset, size);
}
STATIC int
xfs_setfilesize_ioend(
struct xfs_ioend *ioend,
int error)
{
struct xfs_inode *ip = XFS_I(ioend->io_inode);
struct xfs_trans *tp = ioend->io_append_trans;
/*
* The transaction may have been allocated in the I/O submission thread,
* thus we need to mark ourselves as being in a transaction manually.
* Similarly for freeze protection.
*/
current_set_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
__sb_writers_acquired(VFS_I(ip)->i_sb, SB_FREEZE_FS);
/* we abort the update if there was an IO error */
if (error) {
xfs_trans_cancel(tp);
return error;
}
return __xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
}
/*
* IO write completion.
*/
STATIC void
xfs_end_io(
struct work_struct *work)
{
struct xfs_ioend *ioend =
container_of(work, struct xfs_ioend, io_work);
struct xfs_inode *ip = XFS_I(ioend->io_inode);
xfs_off_t offset = ioend->io_offset;
size_t size = ioend->io_size;
int error;
/*
* Just clean up the in-memory strutures if the fs has been shut down.
*/
if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
error = -EIO;
goto done;
}
/*
* Clean up any COW blocks on an I/O error.
*/
error = blk_status_to_errno(ioend->io_bio->bi_status);
if (unlikely(error)) {
switch (ioend->io_type) {
case XFS_IO_COW:
xfs_reflink_cancel_cow_range(ip, offset, size, true);
break;
}
goto done;
}
/*
* Success: commit the COW or unwritten blocks if needed.
*/
switch (ioend->io_type) {
case XFS_IO_COW:
error = xfs_reflink_end_cow(ip, offset, size);
break;
case XFS_IO_UNWRITTEN:
/* writeback should never update isize */
error = xfs_iomap_write_unwritten(ip, offset, size, false);
break;
default:
ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);
break;
}
done:
if (ioend->io_append_trans)
error = xfs_setfilesize_ioend(ioend, error);
xfs_destroy_ioend(ioend, error);
}
STATIC void
xfs_end_bio(
struct bio *bio)
{
struct xfs_ioend *ioend = bio->bi_private;
struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount;
if (ioend->io_type == XFS_IO_UNWRITTEN || ioend->io_type == XFS_IO_COW)
queue_work(mp->m_unwritten_workqueue, &ioend->io_work);
else if (ioend->io_append_trans)
queue_work(mp->m_data_workqueue, &ioend->io_work);
else
xfs_destroy_ioend(ioend, blk_status_to_errno(bio->bi_status));
}
STATIC int
xfs_map_blocks(
struct xfs_writepage_ctx *wpc,
struct inode *inode,
loff_t offset)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
ssize_t count = i_blocksize(inode);
xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset), end_fsb;
struct xfs_bmbt_irec imap;
int whichfork = XFS_DATA_FORK;
int error = 0;
int nimaps = 1;
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
xfs_ilock(ip, XFS_ILOCK_SHARED);
ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
(ip->i_df.if_flags & XFS_IFEXTENTS));
ASSERT(offset <= mp->m_super->s_maxbytes);
if (xfs_is_reflink_inode(ip) &&
xfs_reflink_find_cow_mapping(ip, offset, &imap)) {
xfs_iunlock(ip, XFS_ILOCK_SHARED);
/*
* Truncate can race with writeback since writeback doesn't
* take the iolock and truncate decreases the file size before
* it starts truncating the pages between new_size and old_size.
* Therefore, we can end up in the situation where writeback
* gets a CoW fork mapping but the truncate makes the mapping
* invalid and we end up in here trying to get a new mapping.
* bail out here so that we simply never get a valid mapping
* and so we drop the write altogether. The page truncation
* will kill the contents anyway.
*/
if (offset > i_size_read(inode)) {
wpc->io_type = XFS_IO_HOLE;
return 0;
}
whichfork = XFS_COW_FORK;
wpc->io_type = XFS_IO_COW;
goto allocate_blocks;
}
/*
* Map valid and no COW extent in the way? We're done.
*/
if (wpc->imap_valid) {
xfs_iunlock(ip, XFS_ILOCK_SHARED);
return 0;
}
/*
* If we don't have a valid map, now it's time to get a new one for this
* offset. This will convert delayed allocations (including COW ones)
* into real extents.
*/
if (offset > mp->m_super->s_maxbytes - count)
count = mp->m_super->s_maxbytes - offset;
end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
offset_fsb = XFS_B_TO_FSBT(mp, offset);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
&imap, &nimaps, XFS_BMAPI_ENTIRE);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
if (error)
return error;
if (!nimaps) {
/*
* Lookup returns no match? Beyond eof? regardless,
* return it as a hole so we don't write it
*/
imap.br_startoff = offset_fsb;
imap.br_blockcount = end_fsb - offset_fsb;
imap.br_startblock = HOLESTARTBLOCK;
wpc->io_type = XFS_IO_HOLE;
} else if (imap.br_startblock == HOLESTARTBLOCK) {
/* landed in a hole */
wpc->io_type = XFS_IO_HOLE;
} else {
if (isnullstartblock(imap.br_startblock)) {
/* got a delalloc extent */
wpc->io_type = XFS_IO_DELALLOC;
goto allocate_blocks;
}
if (imap.br_state == XFS_EXT_UNWRITTEN)
wpc->io_type = XFS_IO_UNWRITTEN;
else
wpc->io_type = XFS_IO_OVERWRITE;
}
wpc->imap = imap;
trace_xfs_map_blocks_found(ip, offset, count, wpc->io_type, &imap);
return 0;
allocate_blocks:
error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap);
if (error)
return error;
wpc->imap = imap;
trace_xfs_map_blocks_alloc(ip, offset, count, wpc->io_type, &imap);
return 0;
}
STATIC bool
xfs_imap_valid(
struct inode *inode,
struct xfs_bmbt_irec *imap,
xfs_off_t offset)
{
offset >>= inode->i_blkbits;
/*
* We have to make sure the cached mapping is within EOF to protect
* against eofblocks trimming on file release leaving us with a stale
* mapping. Otherwise, a page for a subsequent file extending buffered
* write could get picked up by this writeback cycle and written to the
* wrong blocks.
*
* Note that what we really want here is a generic mapping invalidation
* mechanism to protect us from arbitrary extent modifying contexts, not
* just eofblocks.
*/
xfs_trim_extent_eof(imap, XFS_I(inode));
return offset >= imap->br_startoff &&
offset < imap->br_startoff + imap->br_blockcount;
}
STATIC void
xfs_start_buffer_writeback(
struct buffer_head *bh)
{
ASSERT(buffer_mapped(bh));
ASSERT(buffer_locked(bh));
ASSERT(!buffer_delay(bh));
ASSERT(!buffer_unwritten(bh));
bh->b_end_io = NULL;
set_buffer_async_write(bh);
set_buffer_uptodate(bh);
clear_buffer_dirty(bh);
}
STATIC void
xfs_start_page_writeback(
struct page *page,
int clear_dirty)
{
ASSERT(PageLocked(page));
ASSERT(!PageWriteback(page));
/*
* if the page was not fully cleaned, we need to ensure that the higher
* layers come back to it correctly. That means we need to keep the page
* dirty, and for WB_SYNC_ALL writeback we need to ensure the
* PAGECACHE_TAG_TOWRITE index mark is not removed so another attempt to
* write this page in this writeback sweep will be made.
*/
if (clear_dirty) {
clear_page_dirty_for_io(page);
set_page_writeback(page);
} else
set_page_writeback_keepwrite(page);
unlock_page(page);
}
static inline int xfs_bio_add_buffer(struct bio *bio, struct buffer_head *bh)
{
return bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
}
/*
* Submit the bio for an ioend. We are passed an ioend with a bio attached to
* it, and we submit that bio. The ioend may be used for multiple bio
* submissions, so we only want to allocate an append transaction for the ioend
* once. In the case of multiple bio submission, each bio will take an IO
* reference to the ioend to ensure that the ioend completion is only done once
* all bios have been submitted and the ioend is really done.
*
* If @fail is non-zero, it means that we have a situation where some part of
* the submission process has failed after we have marked paged for writeback
* and unlocked them. In this situation, we need to fail the bio and ioend
* rather than submit it to IO. This typically only happens on a filesystem
* shutdown.
*/
STATIC int
xfs_submit_ioend(
struct writeback_control *wbc,
struct xfs_ioend *ioend,
int status)
{
/* Convert CoW extents to regular */
if (!status && ioend->io_type == XFS_IO_COW) {
/*
* Yuk. This can do memory allocation, but is not a
* transactional operation so everything is done in GFP_KERNEL
* context. That can deadlock, because we hold pages in
* writeback state and GFP_KERNEL allocations can block on them.
* Hence we must operate in nofs conditions here.
*/
unsigned nofs_flag;
nofs_flag = memalloc_nofs_save();
status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode),
ioend->io_offset, ioend->io_size);
memalloc_nofs_restore(nofs_flag);
}
/* Reserve log space if we might write beyond the on-disk inode size. */
if (!status &&
ioend->io_type != XFS_IO_UNWRITTEN &&
xfs_ioend_is_append(ioend) &&
!ioend->io_append_trans)
status = xfs_setfilesize_trans_alloc(ioend);
ioend->io_bio->bi_private = ioend;
ioend->io_bio->bi_end_io = xfs_end_bio;
ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
/*
* If we are failing the IO now, just mark the ioend with an
* error and finish it. This will run IO completion immediately
* as there is only one reference to the ioend at this point in
* time.
*/
if (status) {
ioend->io_bio->bi_status = errno_to_blk_status(status);
bio_endio(ioend->io_bio);
return status;
}
ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
submit_bio(ioend->io_bio);
return 0;
}
static void
xfs_init_bio_from_bh(
struct bio *bio,
struct buffer_head *bh)
{
bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio_set_dev(bio, bh->b_bdev);
}
static struct xfs_ioend *
xfs_alloc_ioend(
struct inode *inode,
unsigned int type,
xfs_off_t offset,
struct buffer_head *bh)
{
struct xfs_ioend *ioend;
struct bio *bio;
bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, &xfs_ioend_bioset);
xfs_init_bio_from_bh(bio, bh);
ioend = container_of(bio, struct xfs_ioend, io_inline_bio);
INIT_LIST_HEAD(&ioend->io_list);
ioend->io_type = type;
ioend->io_inode = inode;
ioend->io_size = 0;
ioend->io_offset = offset;
INIT_WORK(&ioend->io_work, xfs_end_io);
ioend->io_append_trans = NULL;
ioend->io_bio = bio;
return ioend;
}
/*
* Allocate a new bio, and chain the old bio to the new one.
*
* Note that we have to do perform the chaining in this unintuitive order
* so that the bi_private linkage is set up in the right direction for the
* traversal in xfs_destroy_ioend().
*/
static void
xfs_chain_bio(
struct xfs_ioend *ioend,
struct writeback_control *wbc,
struct buffer_head *bh)
{
struct bio *new;
new = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);
xfs_init_bio_from_bh(new, bh);
bio_chain(ioend->io_bio, new);
bio_get(ioend->io_bio); /* for xfs_destroy_ioend */
ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
submit_bio(ioend->io_bio);
ioend->io_bio = new;
}
/*
* Test to see if we've been building up a completion structure for
* earlier buffers -- if so, we try to append to this ioend if we
* can, otherwise we finish off any current ioend and start another.
* Return the ioend we finished off so that the caller can submit it
* once it has finished processing the dirty page.
*/
STATIC void
xfs_add_to_ioend(
struct inode *inode,
struct buffer_head *bh,
xfs_off_t offset,
struct xfs_writepage_ctx *wpc,
struct writeback_control *wbc,
struct list_head *iolist)
{
if (!wpc->ioend || wpc->io_type != wpc->ioend->io_type ||
bh->b_blocknr != wpc->last_block + 1 ||
offset != wpc->ioend->io_offset + wpc->ioend->io_size) {
if (wpc->ioend)
list_add(&wpc->ioend->io_list, iolist);
wpc->ioend = xfs_alloc_ioend(inode, wpc->io_type, offset, bh);
}
/*
* If the buffer doesn't fit into the bio we need to allocate a new
* one. This shouldn't happen more than once for a given buffer.
*/
while (xfs_bio_add_buffer(wpc->ioend->io_bio, bh) != bh->b_size)
xfs_chain_bio(wpc->ioend, wbc, bh);
wpc->ioend->io_size += bh->b_size;
wpc->last_block = bh->b_blocknr;
xfs_start_buffer_writeback(bh);
}
STATIC void
xfs_map_buffer(
struct inode *inode,
struct buffer_head *bh,
struct xfs_bmbt_irec *imap,
xfs_off_t offset)
{
sector_t bn;
struct xfs_mount *m = XFS_I(inode)->i_mount;
xfs_off_t iomap_offset = XFS_FSB_TO_B(m, imap->br_startoff);
xfs_daddr_t iomap_bn = xfs_fsb_to_db(XFS_I(inode), imap->br_startblock);
ASSERT(imap->br_startblock != HOLESTARTBLOCK);
ASSERT(imap->br_startblock != DELAYSTARTBLOCK);
bn = (iomap_bn >> (inode->i_blkbits - BBSHIFT)) +
((offset - iomap_offset) >> inode->i_blkbits);
ASSERT(bn || XFS_IS_REALTIME_INODE(XFS_I(inode)));
bh->b_blocknr = bn;
set_buffer_mapped(bh);
}
STATIC void
xfs_map_at_offset(
struct inode *inode,
struct buffer_head *bh,
struct xfs_bmbt_irec *imap,
xfs_off_t offset)
{
ASSERT(imap->br_startblock != HOLESTARTBLOCK);
ASSERT(imap->br_startblock != DELAYSTARTBLOCK);
xfs_map_buffer(inode, bh, imap, offset);
set_buffer_mapped(bh);
clear_buffer_delay(bh);
clear_buffer_unwritten(bh);
/*
* If this is a realtime file, data may be on a different device.
* to that pointed to from the buffer_head b_bdev currently. We can't
* trust that the bufferhead has a already been mapped correctly, so
* set the bdev now.
*/
bh->b_bdev = xfs_find_bdev_for_inode(inode);
}
STATIC void
xfs_vm_invalidatepage(
struct page *page,
unsigned int offset,
unsigned int length)
{
trace_xfs_invalidatepage(page->mapping->host, page, offset,
length);
/*
* If we are invalidating the entire page, clear the dirty state from it
* so that we can check for attempts to release dirty cached pages in
* xfs_vm_releasepage().
*/
if (offset == 0 && length >= PAGE_SIZE)
cancel_dirty_page(page);
block_invalidatepage(page, offset, length);
}
/*
* If the page has delalloc buffers on it, we need to punch them out before we
* invalidate the page. If we don't, we leave a stale delalloc mapping on the
* inode that can trip a BUG() in xfs_get_blocks() later on if a direct IO read
* is done on that same region - the delalloc extent is returned when none is
* supposed to be there.
*
* We prevent this by truncating away the delalloc regions on the page before
* invalidating it. Because they are delalloc, we can do this without needing a
* transaction. Indeed - if we get ENOSPC errors, we have to be able to do this
* truncation without a transaction as there is no space left for block
* reservation (typically why we see a ENOSPC in writeback).
*/
STATIC void
xfs_aops_discard_page(
struct page *page)
{
struct inode *inode = page->mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
loff_t offset = page_offset(page);
xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, offset);
int error;
if (XFS_FORCED_SHUTDOWN(mp))
goto out_invalidate;
xfs_alert(mp,
"page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
page, ip->i_ino, offset);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
PAGE_SIZE / i_blocksize(inode));
if (error && !XFS_FORCED_SHUTDOWN(mp))
xfs_alert(mp, "page discard unable to remove delalloc mapping.");
out_invalidate:
xfs_vm_invalidatepage(page, 0, PAGE_SIZE);
}
/*
* We implement an immediate ioend submission policy here to avoid needing to
* chain multiple ioends and hence nest mempool allocations which can violate
* forward progress guarantees we need to provide. The current ioend we are
* adding buffers to is cached on the writepage context, and if the new buffer
* does not append to the cached ioend it will create a new ioend and cache that
* instead.
*
* If a new ioend is created and cached, the old ioend is returned and queued
* locally for submission once the entire page is processed or an error has been
* detected. While ioends are submitted immediately after they are completed,
* batching optimisations are provided by higher level block plugging.
*
* At the end of a writeback pass, there will be a cached ioend remaining on the
* writepage context that the caller will need to submit.
*/
static int
xfs_writepage_map(
struct xfs_writepage_ctx *wpc,
struct writeback_control *wbc,
struct inode *inode,
struct page *page,
uint64_t end_offset)
{
LIST_HEAD(submit_list);
struct xfs_ioend *ioend, *next;
struct buffer_head *bh;
ssize_t len = i_blocksize(inode);
uint64_t file_offset; /* file offset of page */
unsigned poffset; /* offset into page */
int error = 0;
int count = 0;
/*
* Walk the blocks on the page, and if we run off the end of the current
* map or find the current map invalid, grab a new one. We only use
* bufferheads here to check per-block state - they no longer control
* the iteration through the page. This allows us to replace the
* bufferhead with some other state tracking mechanism in future.
*/
file_offset = page_offset(page);
bh = page_buffers(page);
for (poffset = 0;
poffset < PAGE_SIZE;
poffset += len, file_offset += len, bh = bh->b_this_page) {
/* past the range we are writing, so nothing more to write. */
if (file_offset >= end_offset)
break;
if (!buffer_uptodate(bh)) {
if (PageUptodate(page))
ASSERT(buffer_mapped(bh));
continue;
}
if (wpc->imap_valid)
wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap,
file_offset);
/*
* COW fork blocks can overlap data fork blocks even if the
* blocks aren't shared. COW I/O always takes precedent, so we
* must always check for overlap on reflink inodes unless the
* mapping is already a COW one.
*/
if (!wpc->imap_valid ||
(xfs_is_reflink_inode(XFS_I(inode)) &&
wpc->io_type != XFS_IO_COW)) {
error = xfs_map_blocks(wpc, inode, file_offset);
if (error)
goto out;
wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap,
file_offset);
}
if (!wpc->imap_valid || wpc->io_type == XFS_IO_HOLE)
continue;
lock_buffer(bh);
xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
xfs_add_to_ioend(inode, bh, file_offset, wpc, wbc, &submit_list);
count++;
}
ASSERT(wpc->ioend || list_empty(&submit_list));
out:
/*
* On error, we have to fail the ioend here because we have locked
* buffers in the ioend. If we don't do this, we'll deadlock
* invalidating the page as that tries to lock the buffers on the page.
* Also, because we may have set pages under writeback, we have to make
* sure we run IO completion to mark the error state of the IO
* appropriately, so we can't cancel the ioend directly here. That means
* we have to mark this page as under writeback if we included any
* buffers from it in the ioend chain so that completion treats it
* correctly.
*
* If we didn't include the page in the ioend, the on error we can
* simply discard and unlock it as there are no other users of the page
* or it's buffers right now. The caller will still need to trigger
* submission of outstanding ioends on the writepage context so they are
* treated correctly on error.
*/
if (count) {
xfs_start_page_writeback(page, !error);
/*
* Preserve the original error if there was one, otherwise catch
* submission errors here and propagate into subsequent ioend
* submissions.
*/
list_for_each_entry_safe(ioend, next, &submit_list, io_list) {
int error2;
list_del_init(&ioend->io_list);
error2 = xfs_submit_ioend(wbc, ioend, error);
if (error2 && !error)
error = error2;
}
} else if (error) {
xfs_aops_discard_page(page);
ClearPageUptodate(page);
unlock_page(page);
} else {
/*
* We can end up here with no error and nothing to write if we
* race with a partial page truncate on a sub-page block sized
* filesystem. In that case we need to mark the page clean.
*/
xfs_start_page_writeback(page, 1);
end_page_writeback(page);
}
mapping_set_error(page->mapping, error);
return error;
}
/*
* Write out a dirty page.
*
* For delalloc space on the page we need to allocate space and flush it.
* For unwritten space on the page we need to start the conversion to
* regular allocated space.
* For any other dirty buffer heads on the page we should flush them.
*/
STATIC int
xfs_do_writepage(
struct page *page,
struct writeback_control *wbc,
void *data)
{
struct xfs_writepage_ctx *wpc = data;
struct inode *inode = page->mapping->host;
loff_t offset;
uint64_t end_offset;
pgoff_t end_index;
trace_xfs_writepage(inode, page, 0, 0);
ASSERT(page_has_buffers(page));
/*
* Refuse to write the page out if we are called from reclaim context.
*
* This avoids stack overflows when called from deeply used stacks in
* random callers for direct reclaim or memcg reclaim. We explicitly
* allow reclaim from kswapd as the stack usage there is relatively low.
*
* This should never happen except in the case of a VM regression so
* warn about it.
*/
if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
PF_MEMALLOC))
goto redirty;
/*
* Given that we do not allow direct reclaim to call us, we should
* never be called while in a filesystem transaction.
*/
if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS))
goto redirty;
/*
* Is this page beyond the end of the file?
*
* The page index is less than the end_index, adjust the end_offset
* to the highest offset that this page should represent.
* -----------------------------------------------------
* | file mapping | <EOF> |
* -----------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | |
* ^--------------------------------^----------|--------
* | desired writeback range | see else |
* ---------------------------------^------------------|
*/
offset = i_size_read(inode);
end_index = offset >> PAGE_SHIFT;
if (page->index < end_index)
end_offset = (xfs_off_t)(page->index + 1) << PAGE_SHIFT;
else {
/*
* Check whether the page to write out is beyond or straddles
* i_size or not.
* -------------------------------------------------------
* | file mapping | <EOF> |
* -------------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | Beyond |
* ^--------------------------------^-----------|---------
* | | Straddles |
* ---------------------------------^-----------|--------|
*/
unsigned offset_into_page = offset & (PAGE_SIZE - 1);
/*
* Skip the page if it is fully outside i_size, e.g. due to a
* truncate operation that is in progress. We must redirty the
* page so that reclaim stops reclaiming it. Otherwise
* xfs_vm_releasepage() is called on it and gets confused.
*
* Note that the end_index is unsigned long, it would overflow
* if the given offset is greater than 16TB on 32-bit system
* and if we do check the page is fully outside i_size or not
* via "if (page->index >= end_index + 1)" as "end_index + 1"
* will be evaluated to 0. Hence this page will be redirtied
* and be written out repeatedly which would result in an
* infinite loop, the user program that perform this operation
* will hang. Instead, we can verify this situation by checking
* if the page to write is totally beyond the i_size or if it's
* offset is just equal to the EOF.
*/
if (page->index > end_index ||
(page->index == end_index && offset_into_page == 0))
goto redirty;
/*
* The page straddles i_size. It must be zeroed out on each
* and every writepage invocation because it may be mmapped.
* "A file is mapped in multiples of the page size. For a file
* that is not a multiple of the page size, the remaining
* memory is zeroed when mapped, and writes to that region are
* not written out to the file."
*/
zero_user_segment(page, offset_into_page, PAGE_SIZE);
/* Adjust the end_offset to the end of file */
end_offset = offset;
}
return xfs_writepage_map(wpc, wbc, inode, page, end_offset);
redirty:
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
}
STATIC int
xfs_vm_writepage(
struct page *page,
struct writeback_control *wbc)
{
struct xfs_writepage_ctx wpc = {
.io_type = XFS_IO_INVALID,
};
int ret;
ret = xfs_do_writepage(page, wbc, &wpc);
if (wpc.ioend)
ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
return ret;
}
STATIC int
xfs_vm_writepages(
struct address_space *mapping,
struct writeback_control *wbc)
{
struct xfs_writepage_ctx wpc = {
.io_type = XFS_IO_INVALID,
};
int ret;
xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
ret = write_cache_pages(mapping, wbc, xfs_do_writepage, &wpc);
if (wpc.ioend)
ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
return ret;
}
STATIC int
xfs_dax_writepages(
struct address_space *mapping,
struct writeback_control *wbc)
{
xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
return dax_writeback_mapping_range(mapping,
xfs_find_bdev_for_inode(mapping->host), wbc);
}
/*
* Called to move a page into cleanable state - and from there
* to be released. The page should already be clean. We always
* have buffer heads in this call.
*
* Returns 1 if the page is ok to release, 0 otherwise.
*/
STATIC int
xfs_vm_releasepage(
struct page *page,
gfp_t gfp_mask)
{
int delalloc, unwritten;
trace_xfs_releasepage(page->mapping->host, page, 0, 0);
/*
* mm accommodates an old ext3 case where clean pages might not have had
* the dirty bit cleared. Thus, it can send actual dirty pages to
* ->releasepage() via shrink_active_list(). Conversely,
* block_invalidatepage() can send pages that are still marked dirty but
* otherwise have invalidated buffers.
*
* We want to release the latter to avoid unnecessary buildup of the
* LRU, so xfs_vm_invalidatepage() clears the page dirty flag on pages
* that are entirely invalidated and need to be released. Hence the
* only time we should get dirty pages here is through
* shrink_active_list() and so we can simply skip those now.
*
* warn if we've left any lingering delalloc/unwritten buffers on clean
* or invalidated pages we are about to release.
*/
if (PageDirty(page))
return 0;
xfs_count_page_state(page, &delalloc, &unwritten);
if (WARN_ON_ONCE(delalloc))
return 0;
if (WARN_ON_ONCE(unwritten))
return 0;
return try_to_free_buffers(page);
}
/*
* 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.
*
* If the mapping spans EOF, then we have to break the mapping up as the mapping
* for blocks beyond EOF must be marked new so that sub block regions can be
* correctly zeroed. We can't do this for mappings within EOF unless the mapping
* was just allocated or is unwritten, otherwise the callers would overwrite
* existing data with zeros. Hence we have to split the mapping into a range up
* to and including EOF, and a second mapping for beyond EOF.
*/
static void
xfs_map_trim_size(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
struct xfs_bmbt_irec *imap,
xfs_off_t offset,
ssize_t size)
{
xfs_off_t mapping_size;
mapping_size = imap->br_startoff + imap->br_blockcount - iblock;
mapping_size <<= inode->i_blkbits;
ASSERT(mapping_size > 0);
if (mapping_size > size)
mapping_size = size;
if (offset < i_size_read(inode) &&
(xfs_ufsize_t)offset + mapping_size >= i_size_read(inode)) {
/* limit mapping to block that spans EOF */
mapping_size = roundup_64(i_size_read(inode) - offset,
i_blocksize(inode));
}
if (mapping_size > LONG_MAX)
mapping_size = LONG_MAX;
bh_result->b_size = mapping_size;
}
static int
xfs_get_blocks(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
xfs_fileoff_t offset_fsb, end_fsb;
int error = 0;
int lockmode = 0;
struct xfs_bmbt_irec imap;
int nimaps = 1;
xfs_off_t offset;
ssize_t size;
BUG_ON(create);
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
offset = (xfs_off_t)iblock << inode->i_blkbits;
ASSERT(bh_result->b_size >= i_blocksize(inode));
size = bh_result->b_size;
if (offset >= i_size_read(inode))
return 0;
/*
* Direct I/O is usually done on preallocated files, so try getting
* a block mapping without an exclusive lock first.
*/
lockmode = xfs_ilock_data_map_shared(ip);
ASSERT(offset <= mp->m_super->s_maxbytes);
if (offset > mp->m_super->s_maxbytes - size)
size = mp->m_super->s_maxbytes - offset;
end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + size);
offset_fsb = XFS_B_TO_FSBT(mp, offset);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
&nimaps, 0);
if (error)
goto out_unlock;
if (!nimaps) {
trace_xfs_get_blocks_notfound(ip, offset, size);
goto out_unlock;
}
trace_xfs_get_blocks_found(ip, offset, size,
imap.br_state == XFS_EXT_UNWRITTEN ?
XFS_IO_UNWRITTEN : XFS_IO_OVERWRITE, &imap);
xfs_iunlock(ip, lockmode);
/* trim mapping down to size requested */
xfs_map_trim_size(inode, iblock, bh_result, &imap, offset, size);
/*
* For unwritten extents do not report a disk address in the buffered
* read case (treat as if we're reading into a hole).
*/
if (xfs_bmap_is_real_extent(&imap))
xfs_map_buffer(inode, bh_result, &imap, offset);
/*
* 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);
return 0;
out_unlock:
xfs_iunlock(ip, lockmode);
return error;
}
STATIC sector_t
xfs_vm_bmap(
struct address_space *mapping,
sector_t block)
{
struct xfs_inode *ip = XFS_I(mapping->host);
trace_xfs_vm_bmap(ip);
/*
* The swap code (ab-)uses ->bmap to get a block mapping and then
* bypasses the file system for actual I/O. We really can't allow
* that on reflinks inodes, so we have to skip out here. And yes,
* 0 is the magic code for a bmap error.
*
* Since we don't pass back blockdev info, we can't return bmap
* information for rt files either.
*/
if (xfs_is_reflink_inode(ip) || XFS_IS_REALTIME_INODE(ip))
return 0;
return iomap_bmap(mapping, block, &xfs_iomap_ops);
}
STATIC int
xfs_vm_readpage(
struct file *unused,
struct page *page)
{
trace_xfs_vm_readpage(page->mapping->host, 1);
if (i_blocksize(page->mapping->host) == PAGE_SIZE)
return iomap_readpage(page, &xfs_iomap_ops);
return mpage_readpage(page, xfs_get_blocks);
}
STATIC int
xfs_vm_readpages(
struct file *unused,
struct address_space *mapping,
struct list_head *pages,
unsigned nr_pages)
{
trace_xfs_vm_readpages(mapping->host, nr_pages);
if (i_blocksize(mapping->host) == PAGE_SIZE)
return iomap_readpages(mapping, pages, nr_pages, &xfs_iomap_ops);
return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
}
/*
* This is basically a copy of __set_page_dirty_buffers() with one
* small tweak: buffers beyond EOF do not get marked dirty. If we mark them
* dirty, we'll never be able to clean them because we don't write buffers
* beyond EOF, and that means we can't invalidate pages that span EOF
* that have been marked dirty. Further, the dirty state can leak into
* the file interior if the file is extended, resulting in all sorts of
* bad things happening as the state does not match the underlying data.
*
* XXX: this really indicates that bufferheads in XFS need to die. Warts like
* this only exist because of bufferheads and how the generic code manages them.
*/
STATIC int
xfs_vm_set_page_dirty(
struct page *page)
{
struct address_space *mapping = page->mapping;
struct inode *inode = mapping->host;
loff_t end_offset;
loff_t offset;
int newly_dirty;
if (unlikely(!mapping))
return !TestSetPageDirty(page);
end_offset = i_size_read(inode);
offset = page_offset(page);
spin_lock(&mapping->private_lock);
if (page_has_buffers(page)) {
struct buffer_head *head = page_buffers(page);
struct buffer_head *bh = head;
do {
if (offset < end_offset)
set_buffer_dirty(bh);
bh = bh->b_this_page;
offset += i_blocksize(inode);
} while (bh != head);
}
/*
* Lock out page->mem_cgroup migration to keep PageDirty
* synchronized with per-memcg dirty page counters.
*/
lock_page_memcg(page);
newly_dirty = !TestSetPageDirty(page);
spin_unlock(&mapping->private_lock);
if (newly_dirty)
__set_page_dirty(page, mapping, 1);
unlock_page_memcg(page);
if (newly_dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
return newly_dirty;
}
static int
xfs_iomap_swapfile_activate(
struct swap_info_struct *sis,
struct file *swap_file,
sector_t *span)
{
sis->bdev = xfs_find_bdev_for_inode(file_inode(swap_file));
return iomap_swapfile_activate(sis, swap_file, span, &xfs_iomap_ops);
}
const struct address_space_operations xfs_address_space_operations = {
.readpage = xfs_vm_readpage,
.readpages = xfs_vm_readpages,
.writepage = xfs_vm_writepage,
.writepages = xfs_vm_writepages,
.set_page_dirty = xfs_vm_set_page_dirty,
.releasepage = xfs_vm_releasepage,
.invalidatepage = xfs_vm_invalidatepage,
.bmap = xfs_vm_bmap,
.direct_IO = noop_direct_IO,
.migratepage = buffer_migrate_page,
.is_partially_uptodate = block_is_partially_uptodate,
.error_remove_page = generic_error_remove_page,
.swap_activate = xfs_iomap_swapfile_activate,
};
const struct address_space_operations xfs_dax_aops = {
.writepages = xfs_dax_writepages,
.direct_IO = noop_direct_IO,
.set_page_dirty = noop_set_page_dirty,
.invalidatepage = noop_invalidatepage,
.swap_activate = xfs_iomap_swapfile_activate,
};
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