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Subject[PATCH 1/6] f2fs: rework write preallocations
Date
From: Eric Biggers <ebiggers@google.com>

f2fs_write_begin() assumes that all blocks were preallocated by
default unless FI_NO_PREALLOC is explicitly set. This invites data
corruption, as there are cases in which not all blocks are preallocated.
Commit 47501f87c61a ("f2fs: preallocate DIO blocks when forcing
buffered_io") fixed one case, but there are others remaining.

Fix up this logic by replacing this flag with FI_PREALLOCATED_ALL, which
only gets set if all blocks for the current write were preallocated.

Also clean up f2fs_preallocate_blocks(), move it to file.c, and make it
handle some of the logic that was previously in write_iter() directly.

Jaegeuk:
DIO to holes are turning into buffered IO in f2fs_direct_IO, so we should
not preallocate blocks.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/data.c | 55 ++-------------------
fs/f2fs/f2fs.h | 3 +-
fs/f2fs/file.c | 130 +++++++++++++++++++++++++++++++------------------
3 files changed, 87 insertions(+), 101 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 9f754aaef558..3b27fb7daa8b 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1384,53 +1384,6 @@ static int __allocate_data_block(struct dnode_of_data *dn, int seg_type)
return 0;
}

-int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
-{
- struct inode *inode = file_inode(iocb->ki_filp);
- struct f2fs_map_blocks map;
- int flag;
- int err = 0;
- bool direct_io = iocb->ki_flags & IOCB_DIRECT;
-
- map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
- map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
- if (map.m_len > map.m_lblk)
- map.m_len -= map.m_lblk;
- else
- map.m_len = 0;
-
- map.m_next_pgofs = NULL;
- map.m_next_extent = NULL;
- map.m_seg_type = NO_CHECK_TYPE;
- map.m_may_create = true;
-
- if (direct_io) {
- map.m_seg_type = f2fs_rw_hint_to_seg_type(iocb->ki_hint);
- flag = f2fs_force_buffered_io(inode, iocb, from) ?
- F2FS_GET_BLOCK_PRE_AIO :
- F2FS_GET_BLOCK_PRE_DIO;
- goto map_blocks;
- }
- if (iocb->ki_pos + iov_iter_count(from) > MAX_INLINE_DATA(inode)) {
- err = f2fs_convert_inline_inode(inode);
- if (err)
- return err;
- }
- if (f2fs_has_inline_data(inode))
- return err;
-
- flag = F2FS_GET_BLOCK_PRE_AIO;
-
-map_blocks:
- err = f2fs_map_blocks(inode, &map, 1, flag);
- if (map.m_len > 0 && err == -ENOSPC) {
- if (!direct_io)
- set_inode_flag(inode, FI_NO_PREALLOC);
- err = 0;
- }
- return err;
-}
-
void f2fs_do_map_lock(struct f2fs_sb_info *sbi, int flag, bool lock)
{
if (flag == F2FS_GET_BLOCK_PRE_AIO) {
@@ -3339,12 +3292,10 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
int flag;

/*
- * we already allocated all the blocks, so we don't need to get
- * the block addresses when there is no need to fill the page.
+ * If a whole page is being written and we already preallocated all the
+ * blocks, then there is no need to get a block address now.
*/
- if (!f2fs_has_inline_data(inode) && len == PAGE_SIZE &&
- !is_inode_flag_set(inode, FI_NO_PREALLOC) &&
- !f2fs_verity_in_progress(inode))
+ if (len == PAGE_SIZE && is_inode_flag_set(inode, FI_PREALLOCATED_ALL))
return 0;

/* f2fs_lock_op avoids race between write CP and convert_inline_page */
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ce9fc9f13000..be871a79c634 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -715,7 +715,7 @@ enum {
FI_INLINE_DOTS, /* indicate inline dot dentries */
FI_DO_DEFRAG, /* indicate defragment is running */
FI_DIRTY_FILE, /* indicate regular/symlink has dirty pages */
- FI_NO_PREALLOC, /* indicate skipped preallocated blocks */
+ FI_PREALLOCATED_ALL, /* all blocks for write were preallocated */
FI_HOT_DATA, /* indicate file is hot */
FI_EXTRA_ATTR, /* indicate file has extra attribute */
FI_PROJ_INHERIT, /* indicate file inherits projectid */
@@ -3614,7 +3614,6 @@ void f2fs_update_data_blkaddr(struct dnode_of_data *dn, block_t blkaddr);
int f2fs_reserve_new_blocks(struct dnode_of_data *dn, blkcnt_t count);
int f2fs_reserve_new_block(struct dnode_of_data *dn);
int f2fs_get_block(struct dnode_of_data *dn, pgoff_t index);
-int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from);
int f2fs_reserve_block(struct dnode_of_data *dn, pgoff_t index);
struct page *f2fs_get_read_data_page(struct inode *inode, pgoff_t index,
int op_flags, bool for_write);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 92ec2699bc85..4bf77a5bf998 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4235,10 +4235,76 @@ static ssize_t f2fs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
return ret;
}

+/*
+ * Preallocate blocks for a write request, if it is possible and helpful to do
+ * so. Returns a positive number if blocks may have been preallocated, 0 if no
+ * blocks were preallocated, or a negative errno value if something went
+ * seriously wrong. Also sets FI_PREALLOCATED_ALL on the inode if *all* the
+ * requested blocks (not just some of them) have been allocated.
+ */
+static int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *iter)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+ struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+ const loff_t pos = iocb->ki_pos;
+ const size_t count = iov_iter_count(iter);
+ struct f2fs_map_blocks map = {};
+ bool dio = (iocb->ki_flags & IOCB_DIRECT) &&
+ !f2fs_force_buffered_io(inode, iocb, iter);
+ int flag;
+ int ret;
+
+ /* If it will be an out-of-place direct write, don't bother. */
+ if (dio && f2fs_lfs_mode(sbi))
+ return 0;
+
+ /* No-wait I/O can't allocate blocks. */
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ return 0;
+
+ /* If it will be a short write, don't bother. */
+ if (fault_in_iov_iter_readable(iter, count))
+ return 0;
+
+ if (f2fs_has_inline_data(inode)) {
+ /* If the data will fit inline, don't bother. */
+ if (pos + count <= MAX_INLINE_DATA(inode))
+ return 0;
+ ret = f2fs_convert_inline_inode(inode);
+ if (ret)
+ return ret;
+ }
+
+ map.m_lblk = F2FS_BLK_ALIGN(pos);
+ map.m_len = F2FS_BYTES_TO_BLK(pos + count);
+ if (map.m_len > map.m_lblk)
+ map.m_len -= map.m_lblk;
+ else
+ map.m_len = 0;
+ map.m_may_create = true;
+ if (dio) {
+ map.m_seg_type = f2fs_rw_hint_to_seg_type(inode->i_write_hint);
+ flag = F2FS_GET_BLOCK_PRE_DIO;
+ } else {
+ map.m_seg_type = NO_CHECK_TYPE;
+ flag = F2FS_GET_BLOCK_PRE_AIO;
+ }
+
+ ret = f2fs_map_blocks(inode, &map, 1, flag);
+ /* -ENOSPC is only a fatal error if no blocks could be allocated. */
+ if (ret < 0 && !(ret == -ENOSPC && map.m_len > 0))
+ return ret;
+ if (ret == 0)
+ set_inode_flag(inode, FI_PREALLOCATED_ALL);
+ return map.m_len;
+}
+
static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
+ loff_t target_size;
+ int preallocated;
ssize_t ret;

if (unlikely(f2fs_cp_error(F2FS_I_SB(inode)))) {
@@ -4262,84 +4328,54 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)

if (unlikely(IS_IMMUTABLE(inode))) {
ret = -EPERM;
- goto unlock;
+ goto out_unlock;
}

if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
ret = -EPERM;
- goto unlock;
+ goto out_unlock;
}

ret = generic_write_checks(iocb, from);
if (ret > 0) {
- bool preallocated = false;
- size_t target_size = 0;
- int err;
-
- if (fault_in_iov_iter_readable(from, iov_iter_count(from)))
- set_inode_flag(inode, FI_NO_PREALLOC);
-
- if ((iocb->ki_flags & IOCB_NOWAIT)) {
+ if (iocb->ki_flags & IOCB_NOWAIT) {
if (!f2fs_overwrite_io(inode, iocb->ki_pos,
iov_iter_count(from)) ||
f2fs_has_inline_data(inode) ||
f2fs_force_buffered_io(inode, iocb, from)) {
- clear_inode_flag(inode, FI_NO_PREALLOC);
- inode_unlock(inode);
ret = -EAGAIN;
- goto out;
+ goto out_unlock;
}
- goto write;
}
-
- if (is_inode_flag_set(inode, FI_NO_PREALLOC))
- goto write;
-
if (iocb->ki_flags & IOCB_DIRECT) {
- /*
- * Convert inline data for Direct I/O before entering
- * f2fs_direct_IO().
- */
- err = f2fs_convert_inline_inode(inode);
- if (err)
- goto out_err;
- /*
- * If force_buffere_io() is true, we have to allocate
- * blocks all the time, since f2fs_direct_IO will fall
- * back to buffered IO.
- */
- if (!f2fs_force_buffered_io(inode, iocb, from) &&
- f2fs_lfs_mode(F2FS_I_SB(inode)))
- goto write;
+ ret = f2fs_convert_inline_inode(inode);
+ if (ret)
+ goto out_unlock;
}
- preallocated = true;
+ /* Possibly preallocate the blocks for the write. */
target_size = iocb->ki_pos + iov_iter_count(from);
-
- err = f2fs_preallocate_blocks(iocb, from);
- if (err) {
-out_err:
- clear_inode_flag(inode, FI_NO_PREALLOC);
- inode_unlock(inode);
- ret = err;
- goto out;
+ preallocated = f2fs_preallocate_blocks(iocb, from);
+ if (preallocated < 0) {
+ ret = preallocated;
+ goto out_unlock;
}
-write:
+
ret = __generic_file_write_iter(iocb, from);
- clear_inode_flag(inode, FI_NO_PREALLOC);

- /* if we couldn't write data, we should deallocate blocks. */
- if (preallocated && i_size_read(inode) < target_size) {
+ /* Don't leave any preallocated blocks around past i_size. */
+ if (preallocated > 0 && i_size_read(inode) < target_size) {
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
filemap_invalidate_lock(inode->i_mapping);
f2fs_truncate(inode);
filemap_invalidate_unlock(inode->i_mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
}
+ clear_inode_flag(inode, FI_PREALLOCATED_ALL);

if (ret > 0)
f2fs_update_iostat(F2FS_I_SB(inode), APP_WRITE_IO, ret);
}
-unlock:
+out_unlock:
inode_unlock(inode);
out:
trace_f2fs_file_write_iter(inode, iocb->ki_pos,
--
2.34.0.rc1.387.gb447b232ab-goog
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