Commit 55e20bd1 authored by David Sterba's avatar David Sterba

Revert "btrfs: switch to iomap_dio_rw() for dio"

This reverts commit a43a67a2.

This patch reverts the main part of switching direct io implementation
to iomap infrastructure. There's a problem in invalidate page that
couldn't be solved as regression in this development cycle.

The problem occurs when buffered and direct io are mixed, and the ranges
overlap. Although this is not recommended, filesystems implement
measures or fallbacks to make it somehow work. In this case, fallback to
buffered IO would be an option for btrfs (this already happens when
direct io is done on compressed data), but the change would be needed in
the iomap code, bringing new semantics to other filesystems.

Another problem arises when again the buffered and direct ios are mixed,
invalidation fails, then -EIO is set on the mapping and fsync will fail,
though there's no real error.

There have been discussions how to fix that, but revert seems to be the
least intrusive option.

Link: https://lore.kernel.org/linux-btrfs/20200528192103.xm45qoxqmkw7i5yl@fiona/Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent f1084bc6
...@@ -14,7 +14,6 @@ config BTRFS_FS ...@@ -14,7 +14,6 @@ config BTRFS_FS
select LZO_DECOMPRESS select LZO_DECOMPRESS
select ZSTD_COMPRESS select ZSTD_COMPRESS
select ZSTD_DECOMPRESS select ZSTD_DECOMPRESS
select FS_IOMAP
select RAID6_PQ select RAID6_PQ
select XOR_BLOCKS select XOR_BLOCKS
select SRCU select SRCU
......
...@@ -2933,7 +2933,6 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end); ...@@ -2933,7 +2933,6 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start, void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
u64 end, int uptodate); u64 end, int uptodate);
extern const struct dentry_operations btrfs_dentry_operations; extern const struct dentry_operations btrfs_dentry_operations;
ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
/* ioctl.c */ /* ioctl.c */
long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg); long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
......
...@@ -1819,7 +1819,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from) ...@@ -1819,7 +1819,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
loff_t endbyte; loff_t endbyte;
int err; int err;
written = btrfs_direct_IO(iocb, from); written = generic_file_direct_write(iocb, from);
if (written < 0 || !iov_iter_count(from)) if (written < 0 || !iov_iter_count(from))
return written; return written;
...@@ -3476,26 +3476,9 @@ static int btrfs_file_open(struct inode *inode, struct file *filp) ...@@ -3476,26 +3476,9 @@ static int btrfs_file_open(struct inode *inode, struct file *filp)
return generic_file_open(inode, filp); return generic_file_open(inode, filp);
} }
static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
ssize_t ret = 0;
if (iocb->ki_flags & IOCB_DIRECT) {
struct inode *inode = file_inode(iocb->ki_filp);
inode_lock_shared(inode);
ret = btrfs_direct_IO(iocb, to);
inode_unlock_shared(inode);
if (ret < 0)
return ret;
}
return generic_file_buffered_read(iocb, to, ret);
}
const struct file_operations btrfs_file_operations = { const struct file_operations btrfs_file_operations = {
.llseek = btrfs_file_llseek, .llseek = btrfs_file_llseek,
.read_iter = btrfs_file_read_iter, .read_iter = generic_file_read_iter,
.splice_read = generic_file_splice_read, .splice_read = generic_file_splice_read,
.write_iter = btrfs_file_write_iter, .write_iter = btrfs_file_write_iter,
.mmap = btrfs_file_mmap, .mmap = btrfs_file_mmap,
......
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