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SubjectRe: [PATCH] f2fs: Fix direct IO handling
On 26.11.2019 15:44, Jaegeuk Kim wrote:
>On 11/26, Damien Le Moal wrote:
>> f2fs_preallocate_blocks() identifies direct IOs using the IOCB_DIRECT
>> flag for a kiocb structure. However, the file system direct IO handler
>> function f2fs_direct_IO() may have decided that a direct IO has to be
>> exececuted as a buffered IO using the function f2fs_force_buffered_io().
>> This is the case for instance for volumes including zoned block device
>> and for unaligned write IOs with LFS mode enabled.
>>
>> These 2 different methods of identifying direct IOs can result in
>> inconsistencies generating stale data access for direct reads after a
>> direct IO write that is treated as a buffered write. Fix this
>> inconsistency by combining the IOCB_DIRECT flag test with the result
>> of f2fs_force_buffered_io().
>>
>> Reported-by: Javier Gonzalez <javier@javigon.com>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>> fs/f2fs/data.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>> index 5755e897a5f0..8ac2d3b70022 100644
>> --- a/fs/f2fs/data.c
>> +++ b/fs/f2fs/data.c
>> @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>> int flag;
>> int err = 0;
>> bool direct_io = iocb->ki_flags & IOCB_DIRECT;
>> + bool do_direct_io = direct_io &&
>> + !f2fs_force_buffered_io(inode, iocb, from);
>>
>> /* convert inline data for Direct I/O*/
>> if (direct_io) {
>> @@ -1081,7 +1083,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>> return err;
>> }
>>
>> - if (direct_io && allow_outplace_dio(inode, iocb, from))
>> + if (do_direct_io && allow_outplace_dio(inode, iocb, from))
>
>It seems f2fs_force_buffered_io() includes allow_outplace_dio().
>
>How about this?
>---
> fs/f2fs/data.c | 13 -------------
> fs/f2fs/file.c | 35 +++++++++++++++++++++++++----------
> 2 files changed, 25 insertions(+), 23 deletions(-)
>
>diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>index a034cd0ce021..fc40a72f7827 100644
>--- a/fs/f2fs/data.c
>+++ b/fs/f2fs/data.c
>@@ -1180,19 +1180,6 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
> int err = 0;
> bool direct_io = iocb->ki_flags & IOCB_DIRECT;
>
>- /* convert inline data for Direct I/O*/
>- if (direct_io) {
>- err = f2fs_convert_inline_inode(inode);
>- if (err)
>- return err;
>- }
>-
>- if (direct_io && allow_outplace_dio(inode, iocb, from))
>- return 0;
>-
>- if (is_inode_flag_set(inode, FI_NO_PREALLOC))
>- return 0;
>-
> 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)
>diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>index c0560d62dbee..6b32ac6c3382 100644
>--- a/fs/f2fs/file.c
>+++ b/fs/f2fs/file.c
>@@ -3386,18 +3386,33 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> ret = -EAGAIN;
> goto out;
> }
>- } else {
>- preallocated = true;
>- target_size = iocb->ki_pos + iov_iter_count(from);
>+ goto write;
>+ }
>
>- err = f2fs_preallocate_blocks(iocb, from);
>- if (err) {
>- clear_inode_flag(inode, FI_NO_PREALLOC);
>- inode_unlock(inode);
>- ret = err;
>- goto out;
>- }
>+ if (is_inode_flag_set(inode, FI_NO_PREALLOC))
>+ goto write;
>+
>+ if (iocb->ki_flags & IOCB_DIRECT) {
>+ /* convert inline data for Direct I/O*/
>+ err = f2fs_convert_inline_inode(inode);
>+ if (err)
>+ goto out_err;
>+
>+ if (!f2fs_force_buffered_io(inode, iocb, from))
>+ goto write;
>+ }
>+ preallocated = true;
>+ 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;
> }
>+write:
> ret = __generic_file_write_iter(iocb, from);
> clear_inode_flag(inode, FI_NO_PREALLOC);
>
>--
>2.19.0.605.g01d371f741-goog
>
This also addresses the original problem.

Tested-by: Javier González <javier@javigon.com>

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