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NFS: Fix fscache read from NFS after cache error 

Earlier commits refactored some NFS read code and removed
nfs_readpage_async(), but neglected to properly fixup
nfs_readpage_from_fscache_complete().  The code path is
only hit when something unusual occurs with the cachefiles
backing filesystem, such as an IO error or while a cookie
is being invalidated.

Mark page with PG_checked if fscache IO completes in error,
unlock the page, and let the VM decide to re-issue based on
PG_uptodate.  When the VM reissues the readpage, PG_checked
allows us to skip over fscache and read from the server.

Link: https://marc.info/?l=linux-nfs&m=162498209518739
Fixes: 1e83b173b2 ("NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async()")
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Dave Wysochanski 2021-06-29 13:13:57 -04:00 committed by Trond Myklebust
parent e0340f16a0
commit ba512c1bc3
2 changed files with 16 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
fs/nfs/fscache.c
View File

@ -385,12 +385,15 @@ static void nfs_readpage_from_fscache_complete(struct page *page,
"NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",
page, context, error);
/* if the read completes with an error, we just unlock the page and let
* the VM reissue the readpage */
if (!error) {
/*
* If the read completes with an error, mark the page with PG_checked,
* unlock the page, and let the VM reissue the readpage.
*/
if (!error)
SetPageUptodate(page);
unlock_page(page);
}
else
SetPageChecked(page);
unlock_page(page);
}
/*
@ -405,6 +408,11 @@ int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
"NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
nfs_i_fscache(inode), page, page->index, page->flags, inode);
if (PageChecked(page)) {
ClearPageChecked(page);
return 1;
}
ret = fscache_read_or_alloc_page(nfs_i_fscache(inode),
page,
nfs_readpage_from_fscache_complete,

5
fs/nfs/read.c
View File

@ -362,13 +362,13 @@ int nfs_readpage(struct file *file, struct page *page)
} else
desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
xchg(&desc.ctx->error, 0);
if (!IS_SYNC(inode)) {
ret = nfs_readpage_from_fscache(desc.ctx, inode, page);
if (ret == 0)
goto out;
goto out_wait;
}
xchg(&desc.ctx->error, 0);
nfs_pageio_init_read(&desc.pgio, inode, false,
&nfs_async_read_completion_ops);
@ -378,6 +378,7 @@ int nfs_readpage(struct file *file, struct page *page)
nfs_pageio_complete_read(&desc.pgio);
ret = desc.pgio.pg_error < 0 ? desc.pgio.pg_error : 0;
out_wait:
if (!ret) {
ret = wait_on_page_locked_killable(page);
if (!PageUptodate(page) && !ret)