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ext4: Convert ext4_write_begin() to use a folio 

Remove a lot of calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20230324180129.1220691-17-willy@infradead.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Matthew Wilcox 2023-03-24 18:01:16 +00:00 committed by Theodore Ts'o
parent 6b90d4130a
commit 4d934a5e6c
1 changed files with 27 additions and 26 deletions
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53
fs/ext4/inode.c
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@ -1139,7 +1139,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
int ret, needed_blocks;
handle_t *handle;
int retries = 0;
struct page *page;
struct folio *folio;
pgoff_t index;
unsigned from, to;
@ -1166,68 +1166,69 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
}
/*
* grab_cache_page_write_begin() can take a long time if the
* system is thrashing due to memory pressure, or if the page
* __filemap_get_folio() can take a long time if the
* system is thrashing due to memory pressure, or if the folio
* is being written back. So grab it first before we start
* the transaction handle. This also allows us to allocate
* the page (if needed) without using GFP_NOFS.
* the folio (if needed) without using GFP_NOFS.
*/
retry_grab:
page = grab_cache_page_write_begin(mapping, index);
if (!page)
folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
mapping_gfp_mask(mapping));
if (!folio)
return -ENOMEM;
/*
* The same as page allocation, we prealloc buffer heads before
* starting the handle.
*/
if (!page_has_buffers(page))
create_empty_buffers(page, inode->i_sb->s_blocksize, 0);
if (!folio_buffers(folio))
create_empty_buffers(&folio->page, inode->i_sb->s_blocksize, 0);
unlock_page(page);
folio_unlock(folio);
retry_journal:
handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE, needed_blocks);
if (IS_ERR(handle)) {
put_page(page);
folio_put(folio);
return PTR_ERR(handle);
}
lock_page(page);
if (page->mapping != mapping) {
/* The page got truncated from under us */
unlock_page(page);
put_page(page);
folio_lock(folio);
if (folio->mapping != mapping) {
/* The folio got truncated from under us */
folio_unlock(folio);
folio_put(folio);
ext4_journal_stop(handle);
goto retry_grab;
}
/* In case writeback began while the page was unlocked */
wait_for_stable_page(page);
/* In case writeback began while the folio was unlocked */
folio_wait_stable(folio);
#ifdef CONFIG_FS_ENCRYPTION
if (ext4_should_dioread_nolock(inode))
ret = ext4_block_write_begin(page, pos, len,
ret = ext4_block_write_begin(&folio->page, pos, len,
ext4_get_block_unwritten);
else
ret = ext4_block_write_begin(page, pos, len,
ret = ext4_block_write_begin(&folio->page, pos, len,
ext4_get_block);
#else
if (ext4_should_dioread_nolock(inode))
ret = __block_write_begin(page, pos, len,
ret = __block_write_begin(&folio->page, pos, len,
ext4_get_block_unwritten);
else
ret = __block_write_begin(page, pos, len, ext4_get_block);
ret = __block_write_begin(&folio->page, pos, len, ext4_get_block);
#endif
if (!ret && ext4_should_journal_data(inode)) {
ret = ext4_walk_page_buffers(handle, inode,
page_buffers(page), from, to, NULL,
do_journal_get_write_access);
folio_buffers(folio), from, to,
NULL, do_journal_get_write_access);
}
if (ret) {
bool extended = (pos + len > inode->i_size) &&
!ext4_verity_in_progress(inode);
unlock_page(page);
folio_unlock(folio);
/*
* __block_write_begin may have instantiated a few blocks
* outside i_size. Trim these off again. Don't need
@ -1255,10 +1256,10 @@ retry_journal:
if (ret == -ENOSPC &&
ext4_should_retry_alloc(inode->i_sb, &retries))
goto retry_journal;
put_page(page);
folio_put(folio);
return ret;
}
*pagep = page;
*pagep = &folio->page;
return ret;
}