Commit 73c384c0 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: avoid ext4_error()'s caused by ENOMEM in the truncate path 



We can't fail in the truncate path without requiring an fsck.
Add work around for this by using a combination of retry loops
and the __GFP_NOFAIL flag.

From: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAnna Pendleton <pendleton@google.com>
Reviewed-by: default avatarHarshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20200507175028.15061-1-pendleton@google.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 08adf452

fs/ext4/ext4.h

+1 −0
Original line number Diff line number Diff line
@@ -630,6 +630,7 @@ enum { 
 */

#define EXT4_EX_NOCACHE				0x40000000

#define EXT4_EX_FORCE_CACHE			0x20000000

#define EXT4_EX_NOFAIL				0x10000000



/*

 * Flags used by ext4_free_blocks

fs/ext4/extents.c

+33 −10
Original line number Diff line number Diff line
@@ -297,11 +297,14 @@ ext4_force_split_extent_at(handle_t *handle, struct inode *inode, 
{

	struct ext4_ext_path *path = *ppath;

	int unwritten = ext4_ext_is_unwritten(path[path->p_depth].p_ext);

	int flags = EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO;



	if (nofail)

		flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL | EXT4_EX_NOFAIL;



	return ext4_split_extent_at(handle, inode, ppath, lblk, unwritten ?

			EXT4_EXT_MARK_UNWRIT1|EXT4_EXT_MARK_UNWRIT2 : 0,

			EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO |

			(nofail ? EXT4_GET_BLOCKS_METADATA_NOFAIL:0));

			flags);

}



static int
@@ -487,8 +490,12 @@ __read_extent_tree_block(const char *function, unsigned int line, 
{

	struct buffer_head		*bh;

	int				err;

	gfp_t				gfp_flags = __GFP_MOVABLE | GFP_NOFS;



	bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS);

	if (flags & EXT4_EX_NOFAIL)

		gfp_flags |= __GFP_NOFAIL;



	bh = sb_getblk_gfp(inode->i_sb, pblk, gfp_flags);

	if (unlikely(!bh))

		return ERR_PTR(-ENOMEM);
@@ -837,6 +844,10 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block, 
	struct ext4_ext_path *path = orig_path ? *orig_path : NULL;

	short int depth, i, ppos = 0;

	int ret;

	gfp_t gfp_flags = GFP_NOFS;



	if (flags & EXT4_EX_NOFAIL)

		gfp_flags |= __GFP_NOFAIL;



	eh = ext_inode_hdr(inode);

	depth = ext_depth(inode);
@@ -857,7 +868,7 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block, 
	if (!path) {

		/* account possible depth increase */

		path = kcalloc(depth + 2, sizeof(struct ext4_ext_path),

				GFP_NOFS);

				gfp_flags);

		if (unlikely(!path))

			return ERR_PTR(-ENOMEM);

		path[0].p_maxdepth = depth + 1;
@@ -1007,9 +1018,13 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, 
	ext4_fsblk_t newblock, oldblock;

	__le32 border;

	ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */

	gfp_t gfp_flags = GFP_NOFS;

	int err = 0;

	size_t ext_size = 0;



	if (flags & EXT4_EX_NOFAIL)

		gfp_flags |= __GFP_NOFAIL;



	/* make decision: where to split? */

	/* FIXME: now decision is simplest: at current extent */
@@ -1043,7 +1058,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, 
	 * We need this to handle errors and free blocks

	 * upon them.

	 */

	ablocks = kcalloc(depth, sizeof(ext4_fsblk_t), GFP_NOFS);

	ablocks = kcalloc(depth, sizeof(ext4_fsblk_t), gfp_flags);

	if (!ablocks)

		return -ENOMEM;
@@ -2019,7 +2034,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode, 
	if (next != EXT_MAX_BLOCKS) {

		ext_debug("next leaf block - %u\n", next);

		BUG_ON(npath != NULL);

		npath = ext4_find_extent(inode, next, NULL, 0);

		npath = ext4_find_extent(inode, next, NULL, gb_flags);

		if (IS_ERR(npath))

			return PTR_ERR(npath);

		BUG_ON(npath->p_depth != path->p_depth);
@@ -2792,7 +2807,8 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start, 
		ext4_fsblk_t pblk;



		/* find extent for or closest extent to this block */

		path = ext4_find_extent(inode, end, NULL, EXT4_EX_NOCACHE);

		path = ext4_find_extent(inode, end, NULL,

					EXT4_EX_NOCACHE | EXT4_EX_NOFAIL);

		if (IS_ERR(path)) {

			ext4_journal_stop(handle);

			return PTR_ERR(path);
@@ -2878,7 +2894,7 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start, 
				le16_to_cpu(path[k].p_hdr->eh_entries)+1;

	} else {

		path = kcalloc(depth + 1, sizeof(struct ext4_ext_path),

			       GFP_NOFS);

			       GFP_NOFS | __GFP_NOFAIL);

		if (path == NULL) {

			ext4_journal_stop(handle);

			return -ENOMEM;
@@ -3303,7 +3319,7 @@ static int ext4_split_extent(handle_t *handle, 
	 * Update path is required because previous ext4_split_extent_at() may

	 * result in split of original leaf or extent zeroout.

	 */

	path = ext4_find_extent(inode, map->m_lblk, ppath, 0);

	path = ext4_find_extent(inode, map->m_lblk, ppath, flags);

	if (IS_ERR(path))

		return PTR_ERR(path);

	depth = ext_depth(inode);
@@ -4365,7 +4381,14 @@ int ext4_ext_truncate(handle_t *handle, struct inode *inode) 
	}

	if (err)

		return err;

	return ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1);

retry_remove_space:

	err = ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1);

	if (err == -ENOMEM) {

		cond_resched();

		congestion_wait(BLK_RW_ASYNC, HZ/50);

		goto retry_remove_space;

	}

	return err;

}



static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,