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Btrfs: deal with the case that we run out of space in the cache
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Currently we don't handle running out of space in the cache, so to fix this we
keep track of how far in the cache we are.  Then we only dirty the pages if we
successfully modify all of them, otherwise if we have an error or run out of
space we can just drop them and not worry about the vm writing them out.
Thanks,

Tested-by Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>
Signed-off-by: Josef Bacik <josef@redhat.com>
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Josef Bacik committed Apr 8, 2011
1 parent c9ddec7 commit be1a12a
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Showing 3 changed files with 69 additions and 74 deletions.
5 changes: 5 additions & 0 deletions fs/btrfs/ctree.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2576,6 +2576,11 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
struct inode *inode, u64 start, u64 end);
int btrfs_release_file(struct inode *inode, struct file *file);
void btrfs_drop_pages(struct page **pages, size_t num_pages);
int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
struct page **pages, size_t num_pages,
loff_t pos, size_t write_bytes,
struct extent_state **cached);

/* tree-defrag.c */
int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
Expand Down
21 changes: 9 additions & 12 deletions fs/btrfs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
/*
* unlocks pages after btrfs_file_write is done with them
*/
static noinline void btrfs_drop_pages(struct page **pages, size_t num_pages)
void btrfs_drop_pages(struct page **pages, size_t num_pages)
{
size_t i;
for (i = 0; i < num_pages; i++) {
Expand All @@ -127,16 +127,13 @@ static noinline void btrfs_drop_pages(struct page **pages, size_t num_pages)
* this also makes the decision about creating an inline extent vs
* doing real data extents, marking pages dirty and delalloc as required.
*/
static noinline int dirty_and_release_pages(struct btrfs_root *root,
struct file *file,
struct page **pages,
size_t num_pages,
loff_t pos,
size_t write_bytes)
int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
struct page **pages, size_t num_pages,
loff_t pos, size_t write_bytes,
struct extent_state **cached)
{
int err = 0;
int i;
struct inode *inode = fdentry(file)->d_inode;
u64 num_bytes;
u64 start_pos;
u64 end_of_last_block;
Expand All @@ -149,7 +146,7 @@ static noinline int dirty_and_release_pages(struct btrfs_root *root,

end_of_last_block = start_pos + num_bytes - 1;
err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block,
NULL);
cached);
if (err)
return err;

Expand Down Expand Up @@ -992,9 +989,9 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
}

if (copied > 0) {
ret = dirty_and_release_pages(root, file, pages,
dirty_pages, pos,
copied);
ret = btrfs_dirty_pages(root, inode, pages,
dirty_pages, pos, copied,
NULL);
if (ret) {
btrfs_delalloc_release_space(inode,
dirty_pages << PAGE_CACHE_SHIFT);
Expand Down
117 changes: 55 additions & 62 deletions fs/btrfs/free-space-cache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -508,6 +508,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
struct inode *inode;
struct rb_node *node;
struct list_head *pos, *n;
struct page **pages;
struct page *page;
struct extent_state *cached_state = NULL;
struct btrfs_free_cluster *cluster = NULL;
Expand All @@ -517,13 +518,13 @@ int btrfs_write_out_cache(struct btrfs_root *root,
u64 start, end, len;
u64 bytes = 0;
u32 *crc, *checksums;
pgoff_t index = 0, last_index = 0;
unsigned long first_page_offset;
int num_checksums;
int index = 0, num_pages = 0;
int entries = 0;
int bitmaps = 0;
int ret = 0;
bool next_page = false;
bool out_of_space = false;

root = root->fs_info->tree_root;

Expand Down Expand Up @@ -551,24 +552,31 @@ int btrfs_write_out_cache(struct btrfs_root *root,
return 0;
}

last_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
num_pages = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >>
PAGE_CACHE_SHIFT;
filemap_write_and_wait(inode->i_mapping);
btrfs_wait_ordered_range(inode, inode->i_size &
~(root->sectorsize - 1), (u64)-1);

/* We need a checksum per page. */
num_checksums = i_size_read(inode) / PAGE_CACHE_SIZE;
crc = checksums = kzalloc(sizeof(u32) * num_checksums, GFP_NOFS);
crc = checksums = kzalloc(sizeof(u32) * num_pages, GFP_NOFS);
if (!crc) {
iput(inode);
return 0;
}

pages = kzalloc(sizeof(struct page *) * num_pages, GFP_NOFS);
if (!pages) {
kfree(crc);
iput(inode);
return 0;
}

/* Since the first page has all of our checksums and our generation we
* need to calculate the offset into the page that we can start writing
* our entries.
*/
first_page_offset = (sizeof(u32) * num_checksums) + sizeof(u64);
first_page_offset = (sizeof(u32) * num_pages) + sizeof(u64);

/* Get the cluster for this block_group if it exists */
if (!list_empty(&block_group->cluster_list))
Expand All @@ -590,20 +598,18 @@ int btrfs_write_out_cache(struct btrfs_root *root,
* after find_get_page at this point. Just putting this here so people
* know and don't freak out.
*/
while (index <= last_index) {
while (index < num_pages) {
page = grab_cache_page(inode->i_mapping, index);
if (!page) {
pgoff_t i = 0;
int i;

while (i < index) {
page = find_get_page(inode->i_mapping, i);
unlock_page(page);
page_cache_release(page);
page_cache_release(page);
i++;
for (i = 0; i < num_pages; i++) {
unlock_page(pages[i]);
page_cache_release(pages[i]);
}
goto out_free;
}
pages[index] = page;
index++;
}

Expand Down Expand Up @@ -631,7 +637,12 @@ int btrfs_write_out_cache(struct btrfs_root *root,
offset = start_offset;
}

page = find_get_page(inode->i_mapping, index);
if (index >= num_pages) {
out_of_space = true;
break;
}

page = pages[index];

addr = kmap(page);
entry = addr + start_offset;
Expand Down Expand Up @@ -708,23 +719,6 @@ int btrfs_write_out_cache(struct btrfs_root *root,

bytes += PAGE_CACHE_SIZE;

ClearPageChecked(page);
set_page_extent_mapped(page);
SetPageUptodate(page);
set_page_dirty(page);

/*
* We need to release our reference we got for grab_cache_page,
* except for the first page which will hold our checksums, we
* do that below.
*/
if (index != 0) {
unlock_page(page);
page_cache_release(page);
}

page_cache_release(page);

index++;
} while (node || next_page);

Expand All @@ -734,6 +728,10 @@ int btrfs_write_out_cache(struct btrfs_root *root,
struct btrfs_free_space *entry =
list_entry(pos, struct btrfs_free_space, list);

if (index >= num_pages) {
out_of_space = true;
break;
}
page = find_get_page(inode->i_mapping, index);

addr = kmap(page);
Expand All @@ -745,64 +743,58 @@ int btrfs_write_out_cache(struct btrfs_root *root,
crc++;
bytes += PAGE_CACHE_SIZE;

ClearPageChecked(page);
set_page_extent_mapped(page);
SetPageUptodate(page);
set_page_dirty(page);
unlock_page(page);
page_cache_release(page);
page_cache_release(page);
list_del_init(&entry->list);
index++;
}

if (out_of_space) {
btrfs_drop_pages(pages, num_pages);
unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
i_size_read(inode) - 1, &cached_state,
GFP_NOFS);
ret = 0;
goto out_free;
}

/* Zero out the rest of the pages just to make sure */
while (index <= last_index) {
while (index < num_pages) {
void *addr;

page = find_get_page(inode->i_mapping, index);

page = pages[index];
addr = kmap(page);
memset(addr, 0, PAGE_CACHE_SIZE);
kunmap(page);
ClearPageChecked(page);
set_page_extent_mapped(page);
SetPageUptodate(page);
set_page_dirty(page);
unlock_page(page);
page_cache_release(page);
page_cache_release(page);
bytes += PAGE_CACHE_SIZE;
index++;
}

btrfs_set_extent_delalloc(inode, 0, bytes - 1, &cached_state);

/* Write the checksums and trans id to the first page */
{
void *addr;
u64 *gen;

page = find_get_page(inode->i_mapping, 0);
page = pages[0];

addr = kmap(page);
memcpy(addr, checksums, sizeof(u32) * num_checksums);
gen = addr + (sizeof(u32) * num_checksums);
memcpy(addr, checksums, sizeof(u32) * num_pages);
gen = addr + (sizeof(u32) * num_pages);
*gen = trans->transid;
kunmap(page);
ClearPageChecked(page);
set_page_extent_mapped(page);
SetPageUptodate(page);
set_page_dirty(page);
unlock_page(page);
page_cache_release(page);
page_cache_release(page);
}
BTRFS_I(inode)->generation = trans->transid;

ret = btrfs_dirty_pages(root, inode, pages, num_pages, 0,
bytes, &cached_state);
btrfs_drop_pages(pages, num_pages);
unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
i_size_read(inode) - 1, &cached_state, GFP_NOFS);

if (ret) {
ret = 0;
goto out_free;
}

BTRFS_I(inode)->generation = trans->transid;

filemap_write_and_wait(inode->i_mapping);

key.objectid = BTRFS_FREE_SPACE_OBJECTID;
Expand Down Expand Up @@ -853,6 +845,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
BTRFS_I(inode)->generation = 0;
}
kfree(checksums);
kfree(pages);
btrfs_update_inode(trans, root, inode);
iput(inode);
return ret;
Expand Down

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