In subpagesize-blocksize scenario, if i_size occurs in a block which is not
the last block in the page, then the space to be reserved should be calculated
appropriately.
Reviewed-by: Liu Bo <bo.li....@oracle.com>
Signed-off-by: Chandan Rajendra <chan...@linux.vnet.ibm.com>
---
fs/btrfs/inode.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 266f216..294c503 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8661,11 +8661,24 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma,
struct vm_fault *vmf)
loff_t size;
int ret;
int reserved = 0;
+ u64 reserved_space;
u64 page_start;
u64 page_end;
+ u64 end;
+
+ reserved_space = PAGE_CACHE_SIZE;
sb_start_pagefault(inode->i_sb);
- ret = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
+
+ /*
+ * Reserving delalloc space after obtaining the page lock can lead to
+ * deadlock. For example, if a dirty page is locked by this function
+ * and the call to btrfs_delalloc_reserve_space() ends up triggering
+ * dirty page write out, then the btrfs_writepage() function could
+ * end up waiting indefinitely to get a lock on the page currently
+ * being processed by btrfs_page_mkwrite() function.
+ */
+ ret = btrfs_delalloc_reserve_space(inode, reserved_space);
if (!ret) {
ret = file_update_time(vma->vm_file);
reserved = 1;
@@ -8686,6 +8699,7 @@ again:
size = i_size_read(inode);
page_start = page_offset(page);
page_end = page_start + PAGE_CACHE_SIZE - 1;
+ end = page_end;
if ((page->mapping != inode->i_mapping) ||
(page_start >= size)) {
@@ -8701,7 +8715,7 @@ again:
* we can't set the delalloc bits if there are pending ordered
* extents. Drop our locks and wait for them to finish
*/
- ordered = btrfs_lookup_ordered_extent(inode, page_start);
+ ordered = btrfs_lookup_ordered_range(inode, page_start, page_end);
if (ordered) {
unlock_extent_cached(io_tree, page_start, page_end,
&cached_state, GFP_NOFS);
@@ -8711,6 +8725,18 @@ again:
goto again;
}
+ if (page->index == ((size - 1) >> PAGE_CACHE_SHIFT)) {
+ reserved_space = round_up(size - page_start, root->sectorsize);
+ if (reserved_space < PAGE_CACHE_SIZE) {
+ end = page_start + reserved_space - 1;
+ spin_lock(&BTRFS_I(inode)->lock);
+ BTRFS_I(inode)->outstanding_extents++;
+ spin_unlock(&BTRFS_I(inode)->lock);
+ btrfs_delalloc_release_space(inode,
+ PAGE_CACHE_SIZE -
reserved_space);
+ }
+ }
+
/*
* XXX - page_mkwrite gets called every time the page is dirtied, even
* if it was already dirty, so for space accounting reasons we need to
@@ -8718,12 +8744,12 @@ again:
* is probably a better way to do this, but for now keep consistent with
* prepare_pages in the normal write path.
*/
- clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
+ clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, end,
EXTENT_DIRTY | EXTENT_DELALLOC |
EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
0, 0, &cached_state, GFP_NOFS);
- ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
+ ret = btrfs_set_extent_delalloc(inode, page_start, end,
&cached_state);
if (ret) {
unlock_extent_cached(io_tree, page_start, page_end,
@@ -8762,7 +8788,7 @@ out_unlock:
}
unlock_page(page);
out:
- btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
+ btrfs_delalloc_release_space(inode, reserved_space);
out_noreserve:
sb_end_pagefault(inode->i_sb);
return ret;
--
2.1.0
--
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