xfs: implement iomap based buffered write path

Convert XFS to use the new iomap based multipage write path. This involves
implementing the ->iomap_begin and ->iomap_end methods, and switching the
buffered file write, page_mkwrite and xfs_iozero paths to the new iomap
helpers.

With this change __xfs_get_blocks will never be used for buffered writes,
and the code handling them can be removed.

Based on earlier code from Dave Chinner.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2016-06-21 09:53:44 +10:00 committed by Dave Chinner
parent f0c6bcba74
commit 68a9f5e700
7 changed files with 187 additions and 258 deletions

View file

@ -4,6 +4,7 @@ config XFS_FS
depends on (64BIT || LBDAF)
select EXPORTFS
select LIBCRC32C
select FS_IOMAP
help
XFS is a high performance journaling filesystem which originated
on the SGI IRIX platform. It is completely multi-threaded, can

View file

@ -1427,216 +1427,6 @@ xfs_vm_direct_IO(
xfs_get_blocks_direct, endio, NULL, flags);
}
/*
* Punch out the delalloc blocks we have already allocated.
*
* Don't bother with xfs_setattr given that nothing can have made it to disk yet
* as the page is still locked at this point.
*/
STATIC void
xfs_vm_kill_delalloc_range(
struct inode *inode,
loff_t start,
loff_t end)
{
struct xfs_inode *ip = XFS_I(inode);
xfs_fileoff_t start_fsb;
xfs_fileoff_t end_fsb;
int error;
start_fsb = XFS_B_TO_FSB(ip->i_mount, start);
end_fsb = XFS_B_TO_FSB(ip->i_mount, end);
if (end_fsb <= start_fsb)
return;
xfs_ilock(ip, XFS_ILOCK_EXCL);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
end_fsb - start_fsb);
if (error) {
/* something screwed, just bail */
if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
xfs_alert(ip->i_mount,
"xfs_vm_write_failed: unable to clean up ino %lld",
ip->i_ino);
}
}
xfs_iunlock(ip, XFS_ILOCK_EXCL);
}
STATIC void
xfs_vm_write_failed(
struct inode *inode,
struct page *page,
loff_t pos,
unsigned len)
{
loff_t block_offset;
loff_t block_start;
loff_t block_end;
loff_t from = pos & (PAGE_SIZE - 1);
loff_t to = from + len;
struct buffer_head *bh, *head;
struct xfs_mount *mp = XFS_I(inode)->i_mount;
/*
* The request pos offset might be 32 or 64 bit, this is all fine
* on 64-bit platform. However, for 64-bit pos request on 32-bit
* platform, the high 32-bit will be masked off if we evaluate the
* block_offset via (pos & PAGE_MASK) because the PAGE_MASK is
* 0xfffff000 as an unsigned long, hence the result is incorrect
* which could cause the following ASSERT failed in most cases.
* In order to avoid this, we can evaluate the block_offset of the
* start of the page by using shifts rather than masks the mismatch
* problem.
*/
block_offset = (pos >> PAGE_SHIFT) << PAGE_SHIFT;
ASSERT(block_offset + from == pos);
head = page_buffers(page);
block_start = 0;
for (bh = head; bh != head || !block_start;
bh = bh->b_this_page, block_start = block_end,
block_offset += bh->b_size) {
block_end = block_start + bh->b_size;
/* skip buffers before the write */
if (block_end <= from)
continue;
/* if the buffer is after the write, we're done */
if (block_start >= to)
break;
/*
* Process delalloc and unwritten buffers beyond EOF. We can
* encounter unwritten buffers in the event that a file has
* post-EOF unwritten extents and an extending write happens to
* fail (e.g., an unaligned write that also involves a delalloc
* to the same page).
*/
if (!buffer_delay(bh) && !buffer_unwritten(bh))
continue;
if (!xfs_mp_fail_writes(mp) && !buffer_new(bh) &&
block_offset < i_size_read(inode))
continue;
if (buffer_delay(bh))
xfs_vm_kill_delalloc_range(inode, block_offset,
block_offset + bh->b_size);
/*
* This buffer does not contain data anymore. make sure anyone
* who finds it knows that for certain.
*/
clear_buffer_delay(bh);
clear_buffer_uptodate(bh);
clear_buffer_mapped(bh);
clear_buffer_new(bh);
clear_buffer_dirty(bh);
clear_buffer_unwritten(bh);
}
}
/*
* This used to call block_write_begin(), but it unlocks and releases the page
* on error, and we need that page to be able to punch stale delalloc blocks out
* on failure. hence we copy-n-waste it here and call xfs_vm_write_failed() at
* the appropriate point.
*/
STATIC int
xfs_vm_write_begin(
struct file *file,
struct address_space *mapping,
loff_t pos,
unsigned len,
unsigned flags,
struct page **pagep,
void **fsdata)
{
pgoff_t index = pos >> PAGE_SHIFT;
struct page *page;
int status;
struct xfs_mount *mp = XFS_I(mapping->host)->i_mount;
ASSERT(len <= PAGE_SIZE);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
status = __block_write_begin(page, pos, len, xfs_get_blocks);
if (xfs_mp_fail_writes(mp))
status = -EIO;
if (unlikely(status)) {
struct inode *inode = mapping->host;
size_t isize = i_size_read(inode);
xfs_vm_write_failed(inode, page, pos, len);
unlock_page(page);
/*
* If the write is beyond EOF, we only want to kill blocks
* allocated in this write, not blocks that were previously
* written successfully.
*/
if (xfs_mp_fail_writes(mp))
isize = 0;
if (pos + len > isize) {
ssize_t start = max_t(ssize_t, pos, isize);
truncate_pagecache_range(inode, start, pos + len);
}
put_page(page);
page = NULL;
}
*pagep = page;
return status;
}
/*
* On failure, we only need to kill delalloc blocks beyond EOF in the range of
* this specific write because they will never be written. Previous writes
* beyond EOF where block allocation succeeded do not need to be trashed, so
* only new blocks from this write should be trashed. For blocks within
* EOF, generic_write_end() zeros them so they are safe to leave alone and be
* written with all the other valid data.
*/
STATIC int
xfs_vm_write_end(
struct file *file,
struct address_space *mapping,
loff_t pos,
unsigned len,
unsigned copied,
struct page *page,
void *fsdata)
{
int ret;
ASSERT(len <= PAGE_SIZE);
ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
if (unlikely(ret < len)) {
struct inode *inode = mapping->host;
size_t isize = i_size_read(inode);
loff_t to = pos + len;
if (to > isize) {
/* only kill blocks in this write beyond EOF */
if (pos > isize)
isize = pos;
xfs_vm_kill_delalloc_range(inode, isize, to);
truncate_pagecache_range(inode, isize, to);
}
}
return ret;
}
STATIC sector_t
xfs_vm_bmap(
struct address_space *mapping,
@ -1747,8 +1537,6 @@ const struct address_space_operations xfs_address_space_operations = {
.set_page_dirty = xfs_vm_set_page_dirty,
.releasepage = xfs_vm_releasepage,
.invalidatepage = xfs_vm_invalidatepage,
.write_begin = xfs_vm_write_begin,
.write_end = xfs_vm_write_end,
.bmap = xfs_vm_bmap,
.direct_IO = xfs_vm_direct_IO,
.migratepage = buffer_migrate_page,

View file

@ -37,6 +37,7 @@
#include "xfs_log.h"
#include "xfs_icache.h"
#include "xfs_pnfs.h"
#include "xfs_iomap.h"
#include <linux/dcache.h>
#include <linux/falloc.h>
@ -79,57 +80,27 @@ xfs_rw_ilock_demote(
inode_unlock(VFS_I(ip));
}
/*
* xfs_iozero clears the specified range supplied via the page cache (except in
* the DAX case). Writes through the page cache will allocate blocks over holes,
* though the callers usually map the holes first and avoid them. If a block is
* not completely zeroed, then it will be read from disk before being partially
* zeroed.
*
* In the DAX case, we can just directly write to the underlying pages. This
* will not allocate blocks, but will avoid holes and unwritten extents and so
* not do unnecessary work.
*/
int
xfs_iozero(
struct xfs_inode *ip, /* inode */
loff_t pos, /* offset in file */
size_t count) /* size of data to zero */
static int
xfs_dax_zero_range(
struct inode *inode,
loff_t pos,
size_t count)
{
struct page *page;
struct address_space *mapping;
int status = 0;
mapping = VFS_I(ip)->i_mapping;
do {
unsigned offset, bytes;
void *fsdata;
offset = (pos & (PAGE_SIZE -1)); /* Within page */
bytes = PAGE_SIZE - offset;
if (bytes > count)
bytes = count;
if (IS_DAX(VFS_I(ip))) {
status = dax_zero_page_range(VFS_I(ip), pos, bytes,
xfs_get_blocks_direct);
if (status)
break;
} else {
status = pagecache_write_begin(NULL, mapping, pos, bytes,
AOP_FLAG_UNINTERRUPTIBLE,
&page, &fsdata);
if (status)
break;
status = dax_zero_page_range(inode, pos, bytes,
xfs_get_blocks_direct);
if (status)
break;
zero_user(page, offset, bytes);
status = pagecache_write_end(NULL, mapping, pos, bytes,
bytes, page, fsdata);
WARN_ON(status <= 0); /* can't return less than zero! */
status = 0;
}
pos += bytes;
count -= bytes;
} while (count);
@ -137,6 +108,24 @@ xfs_iozero(
return status;
}
/*
* Clear the specified ranges to zero through either the pagecache or DAX.
* Holes and unwritten extents will be left as-is as they already are zeroed.
*/
int
xfs_iozero(
struct xfs_inode *ip,
loff_t pos,
size_t count)
{
struct inode *inode = VFS_I(ip);
if (IS_DAX(VFS_I(ip)))
return xfs_dax_zero_range(inode, pos, count);
else
return iomap_zero_range(inode, pos, count, NULL, &xfs_iomap_ops);
}
int
xfs_update_prealloc_flags(
struct xfs_inode *ip,
@ -841,7 +830,7 @@ xfs_file_buffered_aio_write(
write_retry:
trace_xfs_file_buffered_write(ip, iov_iter_count(from),
iocb->ki_pos, 0);
ret = generic_perform_write(file, from, iocb->ki_pos);
ret = iomap_file_buffered_write(iocb, from, &xfs_iomap_ops);
if (likely(ret >= 0))
iocb->ki_pos += ret;
@ -1553,7 +1542,7 @@ xfs_filemap_page_mkwrite(
if (IS_DAX(inode)) {
ret = __dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault);
} else {
ret = block_page_mkwrite(vma, vmf, xfs_get_blocks);
ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
ret = block_page_mkwrite_return(ret);
}

View file

@ -967,3 +967,147 @@ xfs_bmbt_to_iomap(
iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
}
static inline bool imap_needs_alloc(struct xfs_bmbt_irec *imap, int nimaps)
{
return !nimaps ||
imap->br_startblock == HOLESTARTBLOCK ||
imap->br_startblock == DELAYSTARTBLOCK;
}
static int
xfs_file_iomap_begin(
struct inode *inode,
loff_t offset,
loff_t length,
unsigned flags,
struct iomap *iomap)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
struct xfs_bmbt_irec imap;
xfs_fileoff_t offset_fsb, end_fsb;
int nimaps = 1, error = 0;
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
xfs_ilock(ip, XFS_ILOCK_EXCL);
ASSERT(offset <= mp->m_super->s_maxbytes);
if ((xfs_fsize_t)offset + length > mp->m_super->s_maxbytes)
length = mp->m_super->s_maxbytes - offset;
offset_fsb = XFS_B_TO_FSBT(mp, offset);
end_fsb = XFS_B_TO_FSB(mp, offset + length);
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
&nimaps, XFS_BMAPI_ENTIRE);
if (error) {
xfs_iunlock(ip, XFS_ILOCK_EXCL);
return error;
}
if ((flags & IOMAP_WRITE) && imap_needs_alloc(&imap, nimaps)) {
/*
* We cap the maximum length we map here to MAX_WRITEBACK_PAGES
* pages to keep the chunks of work done where somewhat symmetric
* with the work writeback does. This is a completely arbitrary
* number pulled out of thin air as a best guess for initial
* testing.
*
* Note that the values needs to be less than 32-bits wide until
* the lower level functions are updated.
*/
length = min_t(loff_t, length, 1024 * PAGE_SIZE);
if (xfs_get_extsz_hint(ip)) {
/*
* xfs_iomap_write_direct() expects the shared lock. It
* is unlocked on return.
*/
xfs_ilock_demote(ip, XFS_ILOCK_EXCL);
error = xfs_iomap_write_direct(ip, offset, length, &imap,
nimaps);
} else {
error = xfs_iomap_write_delay(ip, offset, length, &imap);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
}
if (error)
return error;
trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);
xfs_bmbt_to_iomap(ip, iomap, &imap);
} else if (nimaps) {
xfs_iunlock(ip, XFS_ILOCK_EXCL);
trace_xfs_iomap_found(ip, offset, length, 0, &imap);
xfs_bmbt_to_iomap(ip, iomap, &imap);
} else {
xfs_iunlock(ip, XFS_ILOCK_EXCL);
trace_xfs_iomap_not_found(ip, offset, length, 0, &imap);
iomap->blkno = IOMAP_NULL_BLOCK;
iomap->type = IOMAP_HOLE;
iomap->offset = offset;
iomap->length = length;
}
return 0;
}
static int
xfs_file_iomap_end_delalloc(
struct xfs_inode *ip,
loff_t offset,
loff_t length,
ssize_t written)
{
struct xfs_mount *mp = ip->i_mount;
xfs_fileoff_t start_fsb;
xfs_fileoff_t end_fsb;
int error = 0;
start_fsb = XFS_B_TO_FSB(mp, offset + written);
end_fsb = XFS_B_TO_FSB(mp, offset + length);
/*
* Trim back delalloc blocks if we didn't manage to write the whole
* range reserved.
*
* We don't need to care about racing delalloc as we hold i_mutex
* across the reserve/allocate/unreserve calls. If there are delalloc
* blocks in the range, they are ours.
*/
if (start_fsb < end_fsb) {
xfs_ilock(ip, XFS_ILOCK_EXCL);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
end_fsb - start_fsb);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
if (error && !XFS_FORCED_SHUTDOWN(mp)) {
xfs_alert(mp, "%s: unable to clean up ino %lld",
__func__, ip->i_ino);
return error;
}
}
return 0;
}
static int
xfs_file_iomap_end(
struct inode *inode,
loff_t offset,
loff_t length,
ssize_t written,
unsigned flags,
struct iomap *iomap)
{
if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,
length, written);
return 0;
}
struct iomap_ops xfs_iomap_ops = {
.iomap_begin = xfs_file_iomap_begin,
.iomap_end = xfs_file_iomap_end,
};

View file

@ -18,7 +18,8 @@
#ifndef __XFS_IOMAP_H__
#define __XFS_IOMAP_H__
struct iomap;
#include <linux/iomap.h>
struct xfs_inode;
struct xfs_bmbt_irec;
@ -33,4 +34,6 @@ int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t);
void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
struct xfs_bmbt_irec *);
extern struct iomap_ops xfs_iomap_ops;
#endif /* __XFS_IOMAP_H__*/

View file

@ -38,6 +38,7 @@
#include "xfs_dir2.h"
#include "xfs_trans_space.h"
#include "xfs_pnfs.h"
#include "xfs_iomap.h"
#include <linux/capability.h>
#include <linux/xattr.h>
@ -822,8 +823,8 @@ xfs_setattr_size(
error = dax_truncate_page(inode, newsize,
xfs_get_blocks_direct);
} else {
error = block_truncate_page(inode->i_mapping, newsize,
xfs_get_blocks);
error = iomap_truncate_page(inode, newsize,
&did_zeroing, &xfs_iomap_ops);
}
}
@ -838,8 +839,8 @@ xfs_setattr_size(
* problem. Note that this includes any block zeroing we did above;
* otherwise those blocks may not be zeroed after a crash.
*/
if (newsize > ip->i_d.di_size &&
(oldsize != ip->i_d.di_size || did_zeroing)) {
if (did_zeroing ||
(newsize > ip->i_d.di_size && oldsize != ip->i_d.di_size)) {
error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
ip->i_d.di_size, newsize);
if (error)

View file

@ -1295,6 +1295,9 @@ DEFINE_IOMAP_EVENT(xfs_map_blocks_alloc);
DEFINE_IOMAP_EVENT(xfs_get_blocks_found);
DEFINE_IOMAP_EVENT(xfs_get_blocks_alloc);
DEFINE_IOMAP_EVENT(xfs_get_blocks_map_direct);
DEFINE_IOMAP_EVENT(xfs_iomap_alloc);
DEFINE_IOMAP_EVENT(xfs_iomap_found);
DEFINE_IOMAP_EVENT(xfs_iomap_not_found);
DECLARE_EVENT_CLASS(xfs_simple_io_class,
TP_PROTO(struct xfs_inode *ip, xfs_off_t offset, ssize_t count),