Using SEEK_DATA in a huge sparse file can easily lead to sotflockups as
ext4_seek_data() iterates hole block-by-block. Fix the problem by using
returned hole size from ext4_map_blocks() and thus skip the hole in one
go.
Update also SEEK_HOLE implementation to follow the same pattern as
SEEK_DATA to make future maintenance easier.
Furthermore we add cond_resched() to both ext4_seek_data() and
ext4_seek_hole() to avoid softlockups in case evil user creates huge
fragmented file and we have to go through lots of extents.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/ext4.h | 3 ++
fs/ext4/file.c | 97 +++++++++++++++++++++------------------------------------
fs/ext4/inode.c | 67 +++++++++++++++++++++++++++++++++++++++
3 files changed, 106 insertions(+), 61 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 157b458a69d4..f9b1adf9f902 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2559,6 +2559,9 @@ extern void ext4_da_update_reserve_space(struct inode *inode,
int used, int quota_claim);
extern int ext4_issue_zeroout(struct inode *inode, ext4_lblk_t lblk,
ext4_fsblk_t pblk, ext4_lblk_t len);
+extern int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
+ unsigned int map_len,
+ struct extent_status *result);
/* indirect.c */
extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 474f1a4d2ca8..7191095a8ca2 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -432,7 +432,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
*/
static int ext4_find_unwritten_pgoff(struct inode *inode,
int whence,
- struct ext4_map_blocks *map,
+ ext4_lblk_t end_blk,
loff_t *offset)
{
struct pagevec pvec;
@@ -447,7 +447,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
blkbits = inode->i_sb->s_blocksize_bits;
startoff = *offset;
lastoff = startoff;
- endoff = (loff_t)(map->m_lblk + map->m_len) << blkbits;
+ endoff = (loff_t)end_blk << blkbits;
index = startoff >> PAGE_CACHE_SHIFT;
end = endoff >> PAGE_CACHE_SHIFT;
@@ -565,12 +565,11 @@ out:
static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
{
struct inode *inode = file->f_mapping->host;
- struct ext4_map_blocks map;
struct extent_status es;
ext4_lblk_t start, last, end;
loff_t dataoff, isize;
int blkbits;
- int ret = 0;
+ int ret;
inode_lock(inode);
@@ -587,41 +586,32 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
dataoff = offset;
do {
- map.m_lblk = last;
- map.m_len = end - last + 1;
- ret = ext4_map_blocks(NULL, inode, &map, 0);
- if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
- if (last != start)
- dataoff = (loff_t)last << blkbits;
- break;
+ ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
+ if (ret <= 0) {
+ /* No extent found -> no data */
+ if (ret == 0)
+ ret = -ENXIO;
+ inode_unlock(inode);
+ return ret;
}
- /*
- * If there is a delay extent at this offset,
- * it will be as a data.
- */
- ext4_es_find_delayed_extent_range(inode, last, last, &es);
- if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
- if (last != start)
- dataoff = (loff_t)last << blkbits;
+ last = es.es_lblk;
+ if (last != start)
+ dataoff = (loff_t)last << blkbits;
+ if (!ext4_es_is_unwritten(&es))
break;
- }
/*
* If there is a unwritten extent at this offset,
* it will be as a data or a hole according to page
* cache that has data or not.
*/
- if (map.m_flags & EXT4_MAP_UNWRITTEN) {
- int unwritten;
- unwritten = ext4_find_unwritten_pgoff(inode, SEEK_DATA,
- &map, &dataoff);
- if (unwritten)
- break;
- }
-
- last++;
+ if (ext4_find_unwritten_pgoff(inode, SEEK_DATA,
+ es.es_lblk + es.es_len, &dataoff))
+ break;
+ last += es.es_len;
dataoff = (loff_t)last << blkbits;
+ cond_resched();
} while (last <= end);
inode_unlock(inode);
@@ -638,12 +628,11 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
{
struct inode *inode = file->f_mapping->host;
- struct ext4_map_blocks map;
struct extent_status es;
ext4_lblk_t start, last, end;
loff_t holeoff, isize;
int blkbits;
- int ret = 0;
+ int ret;
inode_lock(inode);
@@ -660,44 +649,30 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
holeoff = offset;
do {
- map.m_lblk = last;
- map.m_len = end - last + 1;
- ret = ext4_map_blocks(NULL, inode, &map, 0);
- if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
- last += ret;
- holeoff = (loff_t)last << blkbits;
- continue;
+ ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
+ if (ret < 0) {
+ inode_unlock(inode);
+ return ret;
}
-
- /*
- * If there is a delay extent at this offset,
- * we will skip this extent.
- */
- ext4_es_find_delayed_extent_range(inode, last, last, &es);
- if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
- last = es.es_lblk + es.es_len;
- holeoff = (loff_t)last << blkbits;
- continue;
+ /* Found a hole? */
+ if (ret == 0 || es.es_lblk > last) {
+ if (last != start)
+ holeoff = (loff_t)last << blkbits;
+ break;
}
-
/*
* If there is a unwritten extent at this offset,
* it will be as a data or a hole according to page
* cache that has data or not.
*/
- if (map.m_flags & EXT4_MAP_UNWRITTEN) {
- int unwritten;
- unwritten = ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
- &map, &holeoff);
- if (!unwritten) {
- last += ret;
- holeoff = (loff_t)last << blkbits;
- continue;
- }
- }
+ if (ext4_es_is_unwritten(&es) &&
+ ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
+ last + es.es_len, &holeoff))
+ break;
- /* find a hole */
- break;
+ last += es.es_len;
+ holeoff = (loff_t)last << blkbits;
+ cond_resched();
} while (last <= end);
inode_unlock(inode);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e38c88b37e2e..af7b1e9f7762 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5545,3 +5545,70 @@ int ext4_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
return err;
}
+
+/*
+ * Find the first extent at or after @lblk in an inode that is not a hole.
+ * Search for @map_len blocks at most. The extent is returned in @result.
+ *
+ * The function returns 1 if we found an extent. The function returns 0 in
+ * case there is no extent at or after @lblk and in that case also sets
+ * @result->es_len to 0. In case of error, the error code is returned.
+ */
+int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
+ unsigned int map_len, struct extent_status *result)
+{
+ struct ext4_map_blocks map;
+ struct extent_status es = {};
+ int ret;
+
+ map.m_lblk = lblk;
+ map.m_len = map_len;
+
+ /*
+ * For non-extent based files this loop may iterate several times since
+ * we do not determine full hole size.
+ */
+ while (map.m_len > 0) {
+ ret = ext4_map_blocks(NULL, inode, &map, 0);
+ if (ret < 0)
+ return ret;
+ /* There's extent covering m_lblk? Just return it. */
+ if (ret > 0) {
+ int status;
+
+ ext4_es_store_pblock(result, map.m_pblk);
+ result->es_lblk = map.m_lblk;
+ result->es_len = map.m_len;
+ if (map.m_flags & EXT4_MAP_UNWRITTEN)
+ status = EXTENT_STATUS_UNWRITTEN;
+ else
+ status = EXTENT_STATUS_WRITTEN;
+ ext4_es_store_status(result, status);
+ return 1;
+ }
+ ext4_es_find_delayed_extent_range(inode, map.m_lblk,
+ map.m_lblk + map.m_len - 1,
+ &es);
+ /* Is delalloc data before next block in extent tree? */
+ if (es.es_len && es.es_lblk < map.m_lblk + map.m_len) {
+ ext4_lblk_t offset = 0;
+
+ if (es.es_lblk < lblk)
+ offset = lblk - es.es_lblk;
+ result->es_lblk = es.es_lblk + offset;
+ ext4_es_store_pblock(result,
+ ext4_es_pblock(&es) + offset);
+ result->es_len = es.es_len - offset;
+ ext4_es_store_status(result, ext4_es_status(&es));
+
+ return 1;
+ }
+ /* There's a hole at m_lblk, advance us after it */
+ map.m_lblk += map.m_len;
+ map_len -= map.m_len;
+ map.m_len = map_len;
+ cond_resched();
+ }
+ result->es_len = 0;
+ return 0;
+}
--
2.6.2
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