On Thu 12-10-23 20:55:29, Ritesh Harjani wrote: > Jan Kara <jack@xxxxxxx> writes: > > > Gao Xiang has reported that on ext4 O_SYNC direct IO does not properly > > sync file size update and thus if we crash at unfortunate moment, the > > file can have smaller size although O_SYNC IO has reported successful > > completion. The problem happens because update of on-disk inode size is > > handled in ext4_dio_write_iter() *after* iomap_dio_rw() (and thus > > dio_complete() in particular) has returned and generic_file_sync() gets > > called by dio_complete(). Fix the problem by handling on-disk inode size > > update directly in our ->end_io completion handler. > > > > References: https://lore.kernel.org/all/02d18236-26ef-09b0-90ad-030c4fe3ee20@xxxxxxxxxxxxxxxxx > > Reported-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > Guess we need a fixes tag. Good point, will add. > > --- > > fs/ext4/file.c | 139 ++++++++++++++++++------------------------------- > > 1 file changed, 52 insertions(+), 87 deletions(-) > > > > So finally I've hopefully got all the corner cases right ;) At least fstest > > pass now. > > > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > > index 1492b1ae21f4..d0711c1a9b06 100644 > > --- a/fs/ext4/file.c > > +++ b/fs/ext4/file.c > > @@ -306,80 +306,34 @@ static ssize_t ext4_buffered_write_iter(struct kiocb *iocb, > > } > > > > static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset, > > - ssize_t written, size_t count) > > + ssize_t count) > > { > > handle_t *handle; > > - bool truncate = false; > > - u8 blkbits = inode->i_blkbits; > > - ext4_lblk_t written_blk, end_blk; > > - int ret; > > - > > - /* > > - * Note that EXT4_I(inode)->i_disksize can get extended up to > > - * inode->i_size while the I/O was running due to writeback of delalloc > > - * blocks. But, the code in ext4_iomap_alloc() is careful to use > > - * zeroed/unwritten extents if this is possible; thus we won't leave > > - * uninitialized blocks in a file even if we didn't succeed in writing > > - * as much as we intended. > > - */ > > - WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize); > > - if (offset + count <= EXT4_I(inode)->i_disksize) { > > - /* > > - * We need to ensure that the inode is removed from the orphan > > - * list if it has been added prematurely, due to writeback of > > - * delalloc blocks. > > - */ > > - if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) { > > - handle = ext4_journal_start(inode, EXT4_HT_INODE, 2); > > - > > - if (IS_ERR(handle)) { > > - ext4_orphan_del(NULL, inode); > > - return PTR_ERR(handle); > > - } > > - > > - ext4_orphan_del(handle, inode); > > - ext4_journal_stop(handle); > > - } > > - > > - return written; > > - } > > - > > - if (written < 0) > > - goto truncate; > > > > + lockdep_assert_held_write(&inode->i_rwsem); > > handle = ext4_journal_start(inode, EXT4_HT_INODE, 2); > > - if (IS_ERR(handle)) { > > - written = PTR_ERR(handle); > > - goto truncate; > > - } > > + if (IS_ERR(handle)) > > + return PTR_ERR(handle); > > > > - if (ext4_update_inode_size(inode, offset + written)) { > > - ret = ext4_mark_inode_dirty(handle, inode); > > + if (ext4_update_inode_size(inode, offset + count)) { > > + int ret = ext4_mark_inode_dirty(handle, inode); > > if (unlikely(ret)) { > > - written = ret; > > ext4_journal_stop(handle); > > - goto truncate; > > + return ret; > > } > > } > > > > - /* > > - * We may need to truncate allocated but not written blocks beyond EOF. > > - */ > > - written_blk = ALIGN(offset + written, 1 << blkbits); > > - end_blk = ALIGN(offset + count, 1 << blkbits); > > - if (written_blk < end_blk && ext4_can_truncate(inode)) > > - truncate = true; > > - > > - /* > > - * Remove the inode from the orphan list if it has been extended and > > - * everything went OK. > > - */ > > - if (!truncate && inode->i_nlink) > > + if (inode->i_nlink) > > ext4_orphan_del(handle, inode); > > ext4_journal_stop(handle); > > > > - if (truncate) { > > -truncate: > > + return count; > > +} > > + > > +static void ext4_inode_extension_cleanup(struct inode *inode, ssize_t count) > > +{ > > + lockdep_assert_held_write(&inode->i_rwsem); > > + if (count < 0) { > > ext4_truncate_failed_write(inode); > > /* > > * If the truncate operation failed early, then the inode may > > @@ -388,9 +342,28 @@ static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset, > > */ > > if (inode->i_nlink) > > ext4_orphan_del(NULL, inode); > > + return; > > } > > + /* > > + * If i_disksize got extended due to writeback of delalloc blocks while > > + * the DIO was running we could fail to cleanup the orphan list in > > + * ext4_handle_inode_extension(). Do it now. > > + */ > > + if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) { > > + handle_t *handle = ext4_journal_start(inode, EXT4_HT_INODE, 2); > > > > - return written; > > + if (IS_ERR(handle)) { > > + /* > > + * The write has successfully completed. Not much to > > + * do with the error here so just cleanup the orphan > > + * list and hope for the best. > > + */ > > + ext4_orphan_del(NULL, inode); > > + return; > > + } > > + ext4_orphan_del(handle, inode); > > + ext4_journal_stop(handle); > > + } > > } > > > > static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size, > > @@ -399,31 +372,22 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size, > > loff_t pos = iocb->ki_pos; > > struct inode *inode = file_inode(iocb->ki_filp); > > > > + if (!error && size && flags & IOMAP_DIO_END_UNWRITTEN) > > Do we have IOMAP_DIO_END_UNWRITTEN? or should it be IOMAP_DIO_UNWRITTEN? > Also we don't need to check !error case if we return early in case of an error. It should be IOMAP_DIO_UNWRITTEN. Unrelated iomap cleanup snuck under this patch in my tree (because older versions of the patch needed it). > > + error = ext4_convert_unwritten_extents(NULL, inode, pos, size); > > if (error) > > return error; > > - > > - if (size && flags & IOMAP_DIO_END_UNWRITTEN) { > > ditto. > > > - error = ext4_convert_unwritten_extents(NULL, inode, pos, size); > > - if (error < 0) > > - return error; > > - } > > /* > > - * If we are extending the file, we have to update i_size here before > > - * page cache gets invalidated in iomap_dio_rw(). Otherwise racing > > - * buffered reads could zero out too much from page cache pages. Update > > - * of on-disk size will happen later in ext4_dio_write_iter() where > > - * we have enough information to also perform orphan list handling etc. > > - * Note that we perform all extending writes synchronously under > > - * i_rwsem held exclusively so i_size update is safe here in that case. > > - * If the write was not extending, we cannot see pos > i_size here > > - * because operations reducing i_size like truncate wait for all > > - * outstanding DIO before updating i_size. > > + * Note that EXT4_I(inode)->i_disksize can get extended up to > > + * inode->i_size while the I/O was running due to writeback of delalloc > > + * blocks. But the code in ext4_iomap_alloc() is careful to use > > + * zeroed/unwritten extents if this is possible; thus we won't leave > > + * uninitialized blocks in a file even if we didn't succeed in writing > > + * as much as we intended. > > */ > > - pos += size; > > - if (pos > i_size_read(inode)) > > - i_size_write(inode, pos); > > - > > - return 0; > > + WARN_ON_ONCE(i_size_read(inode) < READ_ONCE(EXT4_I(inode)->i_disksize)); > > + if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize)) > > + return 0; > > + return ext4_handle_inode_extension(inode, pos, size); > > } > > Although it is not a problem, but we are sometimes returning 0 and > sometimes count here. Yeah. iomap_dio_complete() actually fixes this up but I agree it is confusing a bit. Let's return 'size' here. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
