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-rw-r--r--fs/iomap/buffered-io.c756
1 files changed, 665 insertions, 91 deletions
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index e25901ae3ff4..d33c7bc5ee92 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1,7 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2010 Red Hat, Inc.
- * Copyright (c) 2016-2018 Christoph Hellwig.
+ * Copyright (C) 2016-2019 Christoph Hellwig.
*/
#include <linux/module.h>
#include <linux/compiler.h>
@@ -12,13 +12,34 @@
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include <linux/writeback.h>
+#include <linux/list_sort.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/sched/signal.h>
#include <linux/migrate.h>
+#include "trace.h"
#include "../internal.h"
+/*
+ * Structure allocated for each page when block size < PAGE_SIZE to track
+ * sub-page uptodate status and I/O completions.
+ */
+struct iomap_page {
+ atomic_t read_count;
+ atomic_t write_count;
+ DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
+};
+
+static inline struct iomap_page *to_iomap_page(struct page *page)
+{
+ if (page_has_private(page))
+ return (struct iomap_page *)page_private(page);
+ return NULL;
+}
+
+static struct bio_set iomap_ioend_bioset;
+
static struct iomap_page *
iomap_page_create(struct inode *inode, struct page *page)
{
@@ -203,9 +224,17 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
SetPageUptodate(page);
}
+static inline bool iomap_block_needs_zeroing(struct inode *inode,
+ struct iomap *iomap, loff_t pos)
+{
+ return iomap->type != IOMAP_MAPPED ||
+ (iomap->flags & IOMAP_F_NEW) ||
+ pos >= i_size_read(inode);
+}
+
static loff_t
iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct iomap_readpage_ctx *ctx = data;
struct page *page = ctx->cur_page;
@@ -226,7 +255,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
if (plen == 0)
goto done;
- if (iomap->type != IOMAP_MAPPED || pos >= i_size_read(inode)) {
+ if (iomap_block_needs_zeroing(inode, iomap, pos)) {
zero_user(page, poff, plen);
iomap_set_range_uptodate(page, poff, plen);
goto done;
@@ -293,6 +322,8 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops)
unsigned poff;
loff_t ret;
+ trace_iomap_readpage(page->mapping->host, 1);
+
for (poff = 0; poff < PAGE_SIZE; poff += ret) {
ret = iomap_apply(inode, page_offset(page) + poff,
PAGE_SIZE - poff, 0, ops, &ctx,
@@ -351,7 +382,7 @@ iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos,
static loff_t
iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
struct iomap_readpage_ctx *ctx = data;
loff_t done, ret;
@@ -371,7 +402,7 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
ctx->cur_page_in_bio = false;
}
ret = iomap_readpage_actor(inode, pos + done, length - done,
- ctx, iomap);
+ ctx, iomap, srcmap);
}
return done;
@@ -389,6 +420,8 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages,
loff_t last = page_offset(list_entry(pages->next, struct page, lru));
loff_t length = last - pos + PAGE_SIZE, ret = 0;
+ trace_iomap_readpages(mapping->host, nr_pages);
+
while (length > 0) {
ret = iomap_apply(mapping->host, pos, length, 0, ops,
&ctx, iomap_readpages_actor);
@@ -455,6 +488,8 @@ EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
int
iomap_releasepage(struct page *page, gfp_t gfp_mask)
{
+ trace_iomap_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
@@ -470,6 +505,8 @@ EXPORT_SYMBOL_GPL(iomap_releasepage);
void
iomap_invalidatepage(struct page *page, unsigned int offset, unsigned int len)
{
+ trace_iomap_invalidatepage(page->mapping->host, page, offset, len);
+
/*
* If we are invalidating the entire page, clear the dirty state from it
* and release it to avoid unnecessary buildup of the LRU.
@@ -511,6 +548,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage,
EXPORT_SYMBOL_GPL(iomap_migrate_page);
#endif /* CONFIG_MIGRATION */
+enum {
+ IOMAP_WRITE_F_UNSHARE = (1 << 0),
+};
+
static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
@@ -525,19 +566,12 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
}
static int
-iomap_read_page_sync(struct inode *inode, loff_t block_start, struct page *page,
- unsigned poff, unsigned plen, unsigned from, unsigned to,
- struct iomap *iomap)
+iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
+ unsigned plen, struct iomap *iomap)
{
struct bio_vec bvec;
struct bio bio;
- if (iomap->type != IOMAP_MAPPED || block_start >= i_size_read(inode)) {
- zero_user_segments(page, poff, from, to, poff + plen);
- iomap_set_range_uptodate(page, poff, plen);
- return 0;
- }
-
bio_init(&bio, &bvec, 1);
bio.bi_opf = REQ_OP_READ;
bio.bi_iter.bi_sector = iomap_sector(iomap, block_start);
@@ -547,15 +581,15 @@ iomap_read_page_sync(struct inode *inode, loff_t block_start, struct page *page,
}
static int
-__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
- struct page *page, struct iomap *iomap)
+__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
+ struct page *page, struct iomap *srcmap)
{
struct iomap_page *iop = iomap_page_create(inode, page);
loff_t block_size = i_blocksize(inode);
loff_t block_start = pos & ~(block_size - 1);
loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1);
unsigned from = offset_in_page(pos), to = from + len, poff, plen;
- int status = 0;
+ int status;
if (PageUptodate(page))
return 0;
@@ -566,29 +600,39 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
if (plen == 0)
break;
- if ((from > poff && from < poff + plen) ||
- (to > poff && to < poff + plen)) {
- status = iomap_read_page_sync(inode, block_start, page,
- poff, plen, from, to, iomap);
- if (status)
- break;
+ if (!(flags & IOMAP_WRITE_F_UNSHARE) &&
+ (from <= poff || from >= poff + plen) &&
+ (to <= poff || to >= poff + plen))
+ continue;
+
+ if (iomap_block_needs_zeroing(inode, srcmap, block_start)) {
+ if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
+ return -EIO;
+ zero_user_segments(page, poff, from, to, poff + plen);
+ iomap_set_range_uptodate(page, poff, plen);
+ continue;
}
+ status = iomap_read_page_sync(block_start, page, poff, plen,
+ srcmap);
+ if (status)
+ return status;
} while ((block_start += plen) < block_end);
- return status;
+ return 0;
}
static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
- struct page **pagep, struct iomap *iomap)
+ struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
{
const struct iomap_page_ops *page_ops = iomap->page_ops;
- pgoff_t index = pos >> PAGE_SHIFT;
struct page *page;
int status = 0;
BUG_ON(pos + len > iomap->offset + iomap->length);
+ if (srcmap != iomap)
+ BUG_ON(pos + len > srcmap->offset + srcmap->length);
if (fatal_signal_pending(current))
return -EINTR;
@@ -599,18 +643,20 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
return status;
}
- page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
+ page = grab_cache_page_write_begin(inode->i_mapping, pos >> PAGE_SHIFT,
+ AOP_FLAG_NOFS);
if (!page) {
status = -ENOMEM;
goto out_no_page;
}
- if (iomap->type == IOMAP_INLINE)
- iomap_read_inline_data(inode, page, iomap);
+ if (srcmap->type == IOMAP_INLINE)
+ iomap_read_inline_data(inode, page, srcmap);
else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
- status = __block_write_begin_int(page, pos, len, NULL, iomap);
+ status = __block_write_begin_int(page, pos, len, NULL, srcmap);
else
- status = __iomap_write_begin(inode, pos, len, page, iomap);
+ status = __iomap_write_begin(inode, pos, len, flags, page,
+ srcmap);
if (unlikely(status))
goto out_unlock;
@@ -656,7 +702,7 @@ EXPORT_SYMBOL_GPL(iomap_set_page_dirty);
static int
__iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
- unsigned copied, struct page *page, struct iomap *iomap)
+ unsigned copied, struct page *page)
{
flush_dcache_page(page);
@@ -696,20 +742,20 @@ iomap_write_end_inline(struct inode *inode, struct page *page,
}
static int
-iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
- unsigned copied, struct page *page, struct iomap *iomap)
+iomap_write_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied,
+ struct page *page, struct iomap *iomap, struct iomap *srcmap)
{
const struct iomap_page_ops *page_ops = iomap->page_ops;
loff_t old_size = inode->i_size;
int ret;
- if (iomap->type == IOMAP_INLINE) {
+ if (srcmap->type == IOMAP_INLINE) {
ret = iomap_write_end_inline(inode, page, iomap, pos, copied);
- } else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
+ } else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
page, NULL);
} else {
- ret = __iomap_write_end(inode, pos, len, copied, page, iomap);
+ ret = __iomap_write_end(inode, pos, len, copied, page);
}
/*
@@ -736,12 +782,11 @@ iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
static loff_t
iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct iov_iter *i = data;
long status = 0;
ssize_t written = 0;
- unsigned int flags = AOP_FLAG_NOFS;
do {
struct page *page;
@@ -771,8 +816,8 @@ again:
break;
}
- status = iomap_write_begin(inode, pos, bytes, flags, &page,
- iomap);
+ status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap,
+ srcmap);
if (unlikely(status))
break;
@@ -783,8 +828,8 @@ again:
flush_dcache_page(page);
- status = iomap_write_end(inode, pos, bytes, copied, page,
- iomap);
+ status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
+ srcmap);
if (unlikely(status < 0))
break;
copied = status;
@@ -835,50 +880,32 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
-static struct page *
-__iomap_read_page(struct inode *inode, loff_t offset)
-{
- struct address_space *mapping = inode->i_mapping;
- struct page *page;
-
- page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
- if (IS_ERR(page))
- return page;
- if (!PageUptodate(page)) {
- put_page(page);
- return ERR_PTR(-EIO);
- }
- return page;
-}
-
static loff_t
-iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+ struct iomap *iomap, struct iomap *srcmap)
{
long status = 0;
ssize_t written = 0;
- do {
- struct page *page, *rpage;
- unsigned long offset; /* Offset into pagecache page */
- unsigned long bytes; /* Bytes to write to page */
-
- offset = offset_in_page(pos);
- bytes = min_t(loff_t, PAGE_SIZE - offset, length);
+ /* don't bother with blocks that are not shared to start with */
+ if (!(iomap->flags & IOMAP_F_SHARED))
+ return length;
+ /* don't bother with holes or unwritten extents */
+ if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
+ return length;
- rpage = __iomap_read_page(inode, pos);
- if (IS_ERR(rpage))
- return PTR_ERR(rpage);
+ do {
+ unsigned long offset = offset_in_page(pos);
+ unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
+ struct page *page;
status = iomap_write_begin(inode, pos, bytes,
- AOP_FLAG_NOFS, &page, iomap);
- put_page(rpage);
+ IOMAP_WRITE_F_UNSHARE, &page, iomap, srcmap);
if (unlikely(status))
return status;
- WARN_ON_ONCE(!PageUptodate(page));
-
- status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
+ status = iomap_write_end(inode, pos, bytes, bytes, page, iomap,
+ srcmap);
if (unlikely(status <= 0)) {
if (WARN_ON_ONCE(status == 0))
return -EIO;
@@ -898,14 +925,14 @@ iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
}
int
-iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
+iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
const struct iomap_ops *ops)
{
loff_t ret;
while (len) {
ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
- iomap_dirty_actor);
+ iomap_unshare_actor);
if (ret <= 0)
return ret;
pos += ret;
@@ -914,23 +941,22 @@ iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
return 0;
}
-EXPORT_SYMBOL_GPL(iomap_file_dirty);
+EXPORT_SYMBOL_GPL(iomap_file_unshare);
static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
- unsigned bytes, struct iomap *iomap)
+ unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
{
struct page *page;
int status;
- status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
- iomap);
+ status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap, srcmap);
if (status)
return status;
zero_user(page, offset, bytes);
mark_page_accessed(page);
- return iomap_write_end(inode, pos, bytes, bytes, page, iomap);
+ return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
}
static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
@@ -942,14 +968,14 @@ static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
static loff_t
iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
bool *did_zero = data;
loff_t written = 0;
int status;
/* already zeroed? we're done. */
- if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+ if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return count;
do {
@@ -961,7 +987,8 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
if (IS_DAX(inode))
status = iomap_dax_zero(pos, offset, bytes, iomap);
else
- status = iomap_zero(inode, pos, offset, bytes, iomap);
+ status = iomap_zero(inode, pos, offset, bytes, iomap,
+ srcmap);
if (status < 0)
return status;
@@ -1011,7 +1038,7 @@ EXPORT_SYMBOL_GPL(iomap_truncate_page);
static loff_t
iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
struct page *page = data;
int ret;
@@ -1040,20 +1067,19 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
lock_page(page);
size = i_size_read(inode);
- if ((page->mapping != inode->i_mapping) ||
- (page_offset(page) > size)) {
+ offset = page_offset(page);
+ if (page->mapping != inode->i_mapping || offset > size) {
/* We overload EFAULT to mean page got truncated */
ret = -EFAULT;
goto out_unlock;
}
/* page is wholly or partially inside EOF */
- if (((page->index + 1) << PAGE_SHIFT) > size)
+ if (offset > size - PAGE_SIZE)
length = offset_in_page(size);
else
length = PAGE_SIZE;
- offset = page_offset(page);
while (length > 0) {
ret = iomap_apply(inode, offset, length,
IOMAP_WRITE | IOMAP_FAULT, ops, page,
@@ -1071,3 +1097,551 @@ out_unlock:
return block_page_mkwrite_return(ret);
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
+
+static void
+iomap_finish_page_writeback(struct inode *inode, struct page *page,
+ int error)
+{
+ struct iomap_page *iop = to_iomap_page(page);
+
+ if (error) {
+ SetPageError(page);
+ mapping_set_error(inode->i_mapping, -EIO);
+ }
+
+ WARN_ON_ONCE(i_blocksize(inode) < PAGE_SIZE && !iop);
+ WARN_ON_ONCE(iop && atomic_read(&iop->write_count) <= 0);
+
+ if (!iop || atomic_dec_and_test(&iop->write_count))
+ end_page_writeback(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
+iomap_finish_ioend(struct iomap_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 *bv;
+ struct bvec_iter_all iter_all;
+
+ /*
+ * 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(bv, bio, iter_all)
+ iomap_finish_page_writeback(inode, bv->bv_page, error);
+ bio_put(bio);
+ }
+
+ if (unlikely(error && !quiet)) {
+ printk_ratelimited(KERN_ERR
+"%s: writeback error on inode %lu, offset %lld, sector %llu",
+ inode->i_sb->s_id, inode->i_ino, ioend->io_offset,
+ start);
+ }
+}
+
+void
+iomap_finish_ioends(struct iomap_ioend *ioend, int error)
+{
+ struct list_head tmp;
+
+ list_replace_init(&ioend->io_list, &tmp);
+ iomap_finish_ioend(ioend, error);
+
+ while (!list_empty(&tmp)) {
+ ioend = list_first_entry(&tmp, struct iomap_ioend, io_list);
+ list_del_init(&ioend->io_list);
+ iomap_finish_ioend(ioend, error);
+ }
+}
+EXPORT_SYMBOL_GPL(iomap_finish_ioends);
+
+/*
+ * We can merge two adjacent ioends if they have the same set of work to do.
+ */
+static bool
+iomap_ioend_can_merge(struct iomap_ioend *ioend, struct iomap_ioend *next)
+{
+ if (ioend->io_bio->bi_status != next->io_bio->bi_status)
+ return false;
+ if ((ioend->io_flags & IOMAP_F_SHARED) ^
+ (next->io_flags & IOMAP_F_SHARED))
+ return false;
+ if ((ioend->io_type == IOMAP_UNWRITTEN) ^
+ (next->io_type == IOMAP_UNWRITTEN))
+ return false;
+ if (ioend->io_offset + ioend->io_size != next->io_offset)
+ return false;
+ return true;
+}
+
+void
+iomap_ioend_try_merge(struct iomap_ioend *ioend, struct list_head *more_ioends,
+ void (*merge_private)(struct iomap_ioend *ioend,
+ struct iomap_ioend *next))
+{
+ struct iomap_ioend *next;
+
+ INIT_LIST_HEAD(&ioend->io_list);
+
+ while ((next = list_first_entry_or_null(more_ioends, struct iomap_ioend,
+ io_list))) {
+ if (!iomap_ioend_can_merge(ioend, next))
+ break;
+ list_move_tail(&next->io_list, &ioend->io_list);
+ ioend->io_size += next->io_size;
+ if (next->io_private && merge_private)
+ merge_private(ioend, next);
+ }
+}
+EXPORT_SYMBOL_GPL(iomap_ioend_try_merge);
+
+static int
+iomap_ioend_compare(void *priv, struct list_head *a, struct list_head *b)
+{
+ struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list);
+ struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list);
+
+ if (ia->io_offset < ib->io_offset)
+ return -1;
+ if (ia->io_offset > ib->io_offset)
+ return 1;
+ return 0;
+}
+
+void
+iomap_sort_ioends(struct list_head *ioend_list)
+{
+ list_sort(NULL, ioend_list, iomap_ioend_compare);
+}
+EXPORT_SYMBOL_GPL(iomap_sort_ioends);
+
+static void iomap_writepage_end_bio(struct bio *bio)
+{
+ struct iomap_ioend *ioend = bio->bi_private;
+
+ iomap_finish_ioend(ioend, blk_status_to_errno(bio->bi_status));
+}
+
+/*
+ * Submit the final bio for an ioend.
+ *
+ * If @error 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 instead of
+ * submitting it. This typically only happens on a filesystem shutdown.
+ */
+static int
+iomap_submit_ioend(struct iomap_writepage_ctx *wpc, struct iomap_ioend *ioend,
+ int error)
+{
+ ioend->io_bio->bi_private = ioend;
+ ioend->io_bio->bi_end_io = iomap_writepage_end_bio;
+
+ if (wpc->ops->prepare_ioend)
+ error = wpc->ops->prepare_ioend(ioend, error);
+ if (error) {
+ /*
+ * 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.
+ */
+ ioend->io_bio->bi_status = errno_to_blk_status(error);
+ bio_endio(ioend->io_bio);
+ return error;
+ }
+
+ submit_bio(ioend->io_bio);
+ return 0;
+}
+
+static struct iomap_ioend *
+iomap_alloc_ioend(struct inode *inode, struct iomap_writepage_ctx *wpc,
+ loff_t offset, sector_t sector, struct writeback_control *wbc)
+{
+ struct iomap_ioend *ioend;
+ struct bio *bio;
+
+ bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, &iomap_ioend_bioset);
+ bio_set_dev(bio, wpc->iomap.bdev);
+ bio->bi_iter.bi_sector = sector;
+ bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
+ bio->bi_write_hint = inode->i_write_hint;
+ wbc_init_bio(wbc, bio);
+
+ ioend = container_of(bio, struct iomap_ioend, io_inline_bio);
+ INIT_LIST_HEAD(&ioend->io_list);
+ ioend->io_type = wpc->iomap.type;
+ ioend->io_flags = wpc->iomap.flags;
+ ioend->io_inode = inode;
+ ioend->io_size = 0;
+ ioend->io_offset = offset;
+ ioend->io_private = 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 iomap_finish_ioend().
+ */
+static struct bio *
+iomap_chain_bio(struct bio *prev)
+{
+ struct bio *new;
+
+ new = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);
+ bio_copy_dev(new, prev);/* also copies over blkcg information */
+ new->bi_iter.bi_sector = bio_end_sector(prev);
+ new->bi_opf = prev->bi_opf;
+ new->bi_write_hint = prev->bi_write_hint;
+
+ bio_chain(prev, new);
+ bio_get(prev); /* for iomap_finish_ioend */
+ submit_bio(prev);
+ return new;
+}
+
+static bool
+iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t offset,
+ sector_t sector)
+{
+ if ((wpc->iomap.flags & IOMAP_F_SHARED) !=
+ (wpc->ioend->io_flags & IOMAP_F_SHARED))
+ return false;
+ if (wpc->iomap.type != wpc->ioend->io_type)
+ return false;
+ if (offset != wpc->ioend->io_offset + wpc->ioend->io_size)
+ return false;
+ if (sector != bio_end_sector(wpc->ioend->io_bio))
+ return false;
+ return true;
+}
+
+/*
+ * Test to see if we have an existing ioend structure that we could append to
+ * first, otherwise finish off the current ioend and start another.
+ */
+static void
+iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page,
+ struct iomap_page *iop, struct iomap_writepage_ctx *wpc,
+ struct writeback_control *wbc, struct list_head *iolist)
+{
+ sector_t sector = iomap_sector(&wpc->iomap, offset);
+ unsigned len = i_blocksize(inode);
+ unsigned poff = offset & (PAGE_SIZE - 1);
+ bool merged, same_page = false;
+
+ if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, offset, sector)) {
+ if (wpc->ioend)
+ list_add(&wpc->ioend->io_list, iolist);
+ wpc->ioend = iomap_alloc_ioend(inode, wpc, offset, sector, wbc);
+ }
+
+ merged = __bio_try_merge_page(wpc->ioend->io_bio, page, len, poff,
+ &same_page);
+ if (iop && !same_page)
+ atomic_inc(&iop->write_count);
+
+ if (!merged) {
+ if (bio_full(wpc->ioend->io_bio, len)) {
+ wpc->ioend->io_bio =
+ iomap_chain_bio(wpc->ioend->io_bio);
+ }
+ bio_add_page(wpc->ioend->io_bio, page, len, poff);
+ }
+
+ wpc->ioend->io_size += len;
+ wbc_account_cgroup_owner(wbc, page, len);
+}
+
+/*
+ * 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 blocks to is cached on the writepage context, and if the new block
+ * 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
+iomap_writepage_map(struct iomap_writepage_ctx *wpc,
+ struct writeback_control *wbc, struct inode *inode,
+ struct page *page, u64 end_offset)
+{
+ struct iomap_page *iop = to_iomap_page(page);
+ struct iomap_ioend *ioend, *next;
+ unsigned len = i_blocksize(inode);
+ u64 file_offset; /* file offset of page */
+ int error = 0, count = 0, i;
+ LIST_HEAD(submit_list);
+
+ WARN_ON_ONCE(i_blocksize(inode) < PAGE_SIZE && !iop);
+ WARN_ON_ONCE(iop && atomic_read(&iop->write_count) != 0);
+
+ /*
+ * Walk through the page to find areas to write back. If we run off the
+ * end of the current map or find the current map invalid, grab a new
+ * one.
+ */
+ for (i = 0, file_offset = page_offset(page);
+ i < (PAGE_SIZE >> inode->i_blkbits) && file_offset < end_offset;
+ i++, file_offset += len) {
+ if (iop && !test_bit(i, iop->uptodate))
+ continue;
+
+ error = wpc->ops->map_blocks(wpc, inode, file_offset);
+ if (error)
+ break;
+ if (WARN_ON_ONCE(wpc->iomap.type == IOMAP_INLINE))
+ continue;
+ if (wpc->iomap.type == IOMAP_HOLE)
+ continue;
+ iomap_add_to_ioend(inode, file_offset, page, iop, wpc, wbc,
+ &submit_list);
+ count++;
+ }
+
+ WARN_ON_ONCE(!wpc->ioend && !list_empty(&submit_list));
+ WARN_ON_ONCE(!PageLocked(page));
+ WARN_ON_ONCE(PageWriteback(page));
+
+ /*
+ * We cannot cancel the ioend directly here on error. We may have
+ * already set other pages under writeback and hence we have to run I/O
+ * completion to mark the error state of the pages under writeback
+ * appropriately.
+ */
+ if (unlikely(error)) {
+ if (!count) {
+ /*
+ * If the current page hasn't been added to ioend, it
+ * won't be affected by I/O completions and we must
+ * discard and unlock it right here.
+ */
+ if (wpc->ops->discard_page)
+ wpc->ops->discard_page(page);
+ ClearPageUptodate(page);
+ unlock_page(page);
+ goto done;
+ }
+
+ /*
+ * 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.
+ */
+ set_page_writeback_keepwrite(page);
+ } else {
+ clear_page_dirty_for_io(page);
+ set_page_writeback(page);
+ }
+
+ unlock_page(page);
+
+ /*
+ * 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 = iomap_submit_ioend(wpc, ioend, error);
+ if (error2 && !error)
+ error = error2;
+ }
+
+ /*
+ * We can end up here with no error and nothing to write only if we race
+ * with a partial page truncate on a sub-page block sized filesystem.
+ */
+ if (!count)
+ end_page_writeback(page);
+done:
+ 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.
+ */
+static int
+iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
+{
+ struct iomap_writepage_ctx *wpc = data;
+ struct inode *inode = page->mapping->host;
+ pgoff_t end_index;
+ u64 end_offset;
+ loff_t offset;
+
+ trace_iomap_writepage(inode, page, 0, 0);
+
+ /*
+ * 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 in a recursive filesystem reclaim context.
+ */
+ 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 = (loff_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
+ * iomap_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 iomap_writepage_map(wpc, wbc, inode, page, end_offset);
+
+redirty:
+ redirty_page_for_writepage(wbc, page);
+ unlock_page(page);
+ return 0;
+}
+
+int
+iomap_writepage(struct page *page, struct writeback_control *wbc,
+ struct iomap_writepage_ctx *wpc,
+ const struct iomap_writeback_ops *ops)
+{
+ int ret;
+
+ wpc->ops = ops;
+ ret = iomap_do_writepage(page, wbc, wpc);
+ if (!wpc->ioend)
+ return ret;
+ return iomap_submit_ioend(wpc, wpc->ioend, ret);
+}
+EXPORT_SYMBOL_GPL(iomap_writepage);
+
+int
+iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
+ struct iomap_writepage_ctx *wpc,
+ const struct iomap_writeback_ops *ops)
+{
+ int ret;
+
+ wpc->ops = ops;
+ ret = write_cache_pages(mapping, wbc, iomap_do_writepage, wpc);
+ if (!wpc->ioend)
+ return ret;
+ return iomap_submit_ioend(wpc, wpc->ioend, ret);
+}
+EXPORT_SYMBOL_GPL(iomap_writepages);
+
+static int __init iomap_init(void)
+{
+ return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
+ offsetof(struct iomap_ioend, io_inline_bio),
+ BIOSET_NEED_BVECS);
+}
+fs_initcall(iomap_init);