Re: [PATCH v3 0/3] data integrity: Stabilize pages during writeback for ext4
From: Jan Kara <jack@suse.cz>
Date: 2011-05-05 15:26:01
Also in:
linux-fsdevel, linux-scsi, lkml
Hello, On Wed 04-05-11 16:57:06, Darrick J. Wong wrote:
On Wed, May 04, 2011 at 03:21:55PM -0400, Chris Mason wrote:quoted
Excerpts from Christoph Hellwig's message of 2011-05-04 14:46:44 -0400:quoted
This seems to miss out on a lot of the generic functionality like write_cache_pages and block_page_mkwrite and just patch it into the ext4 copy & paste variants. Please make sure your patches also work for filesystem that use more of the generic functionality like xfs or ext2 (the latter one might be fun for the mmap case).Probably after the block_commit_write in block_page_mkwrite() Another question is, do we want to introduce a wait_on_stable_page_writeback()?Something like this here? It fixes block_page_mkwrite users and sticks in a simple page_mkwrite for fses that don't provide one at all. From a quick wac run it seems to make xfs work. ext2 seems to have some issues with modifying a buffer_head's bh_data without locking the bh during the update, so I guess it needs some review.
Yes, ext2 is rather difficult because of all the metadata updates to buffers happening. That would need a serious work I suspect.
quoted hunk ↗ jump to hunk
fs: Modify/provide generic writepage/page_mkwrite functions to wait for writeback Modify the generic writepage function, and add an empty page_mkwrite function, to wait for page writeback to finish before allowing writes. This is so that simple filesystems have stable pages during write operations. Signed-off-by: Darrick J. Wong <redacted> --- fs/buffer.c | 1 + mm/filemap.c | 10 ++++++++++ 2 files changed, 11 insertions(+), 0 deletions(-)diff --git a/fs/buffer.c b/fs/buffer.c index a08bb8e..cf9a795 100644 --- a/fs/buffer.c +++ b/fs/buffer.c@@ -2361,6 +2361,7 @@ block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, if (!ret) ret = block_commit_write(page, 0, end); + wait_on_page_writeback(page); if (unlikely(ret)) { unlock_page(page); if (ret == -ENOMEM)diff --git a/mm/filemap.c b/mm/filemap.c index c22675f..9cb4e51 100644 --- a/mm/filemap.c +++ b/mm/filemap.c@@ -1713,8 +1713,18 @@ page_not_uptodate: } EXPORT_SYMBOL(filemap_fault); +static int empty_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct page *page = vmf->page; + + lock_page(page); + wait_on_page_writeback(page); + return VM_FAULT_LOCKED; +} +
I guess you miss the whether the page has been truncated here (in which case you should return VM_FAULT_NOPAGE).
const struct vm_operations_struct generic_file_vm_ops = {
.fault = filemap_fault,
+ .page_mkwrite = empty_page_mkwrite,
};
/* This is used for a general mmap of a disk file */Honza -- Jan Kara [off-list ref] SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>