2018-01-03 10:08:44

by Jan Kara

Subject: [PATCH 2/2] ext4: Fix ENOSPC handling in DAX page fault handler

When allocation of underlying block for a page fault fails, we fail the
fault with SIGBUS. However we may well hit ENOSPC just due to lots of
free blocks being held by the running / committing transaction. So
propagate the error from ext4_iomap_begin() and implement do standard
allocation retry loop in ext4_dax_huge_fault().

Reviewed-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/[email protected]>
Signed-off-by: Jan Kara <[email protected]>
---
fs/ext4/file.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1c7cd882d998..fb6f023622fe 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -280,7 +280,8 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
static int ext4_dax_huge_fault(struct vm_fault *vmf,
enum page_entry_size pe_size)
{
- int result;
+ int result, error = 0;
+ int retries = 0;
handle_t *handle = NULL;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct super_block *sb = inode->i_sb;
@@ -304,6 +305,7 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
sb_start_pagefault(sb);
file_update_time(vmf->vma->vm_file);
down_read(&EXT4_I(inode)->i_mmap_sem);
+retry:
handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
EXT4_DATA_TRANS_BLOCKS(sb));
if (IS_ERR(handle)) {
@@ -314,9 +316,13 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
} else {
down_read(&EXT4_I(inode)->i_mmap_sem);
}
- result = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &ext4_iomap_ops);
+ result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
if (write) {
ext4_journal_stop(handle);
+
+ if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
+ ext4_should_retry_alloc(sb, &retries))
+ goto retry;
/* Handling synchronous page fault? */
if (result & VM_FAULT_NEEDDSYNC)
result = dax_finish_sync_fault(vmf, pe_size, pfn);
--
2.12.3

2018-01-07 21:51:37

by Theodore Ts'o

Subject: Re: [PATCH 2/2] ext4: Fix ENOSPC handling in DAX page fault handler

On Wed, Jan 03, 2018 at 11:08:44AM +0100, Jan Kara wrote:
> When allocation of underlying block for a page fault fails, we fail the
> fault with SIGBUS. However we may well hit ENOSPC just due to lots of
> free blocks being held by the running / committing transaction. So
> propagate the error from ext4_iomap_begin() and implement do standard
> allocation retry loop in ext4_dax_huge_fault().
>
> Reviewed-by: Ross Zwisler <[email protected]>
> Signed-off-by: Jan Kara <[email protected]>

Applied, thanks.

- Ted