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ext4 crypto: don't let data integrity writebacks fail with ENOMEM

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We don't want the writeback triggered from the journal commit (in
data=writeback mode) to cause the journal to abort due to
generic_writepages() returning an ENOMEM error.  In addition, if
fsync() fails with ENOMEM, most applications will probably not do the
right thing.

So if we are doing a data integrity sync, and ext4_encrypt() returns
ENOMEM, we will submit any queued I/O to date, and then retry the
allocation using GFP_NOFAIL.

Google-Bug-Id: 27641567

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2016-03-26 16:14:34 -04:00
parent 9e92f48c34
commit c9af28fdd4
4 changed files with 39 additions and 20 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

37
fs/ext4/crypto.c
View file

@ -91,7 +91,8 @@ void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
* Return: An allocated and initialized encryption context on success; error * Return: An allocated and initialized encryption context on success; error
* value or NULL otherwise. * value or NULL otherwise.
*/ */
struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode) struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode,
gfp_t gfp_flags)
{ {
struct ext4_crypto_ctx *ctx = NULL; struct ext4_crypto_ctx *ctx = NULL;
int res = 0; int res = 0;
@ -118,7 +119,7 @@ struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
list_del(&ctx->free_list); list_del(&ctx->free_list);
spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags); spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
if (!ctx) { if (!ctx) {
ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS); ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, gfp_flags);
if (!ctx) { if (!ctx) {
res = -ENOMEM; res = -ENOMEM;
goto out; goto out;
@ -255,7 +256,8 @@ static int ext4_page_crypto(struct inode *inode,
ext4_direction_t rw, ext4_direction_t rw,
pgoff_t index, pgoff_t index,
struct page *src_page, struct page *src_page,
struct page *dest_page) struct page *dest_page,
gfp_t gfp_flags)
{ {
u8 xts_tweak[EXT4_XTS_TWEAK_SIZE]; u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
@ -266,7 +268,7 @@ static int ext4_page_crypto(struct inode *inode,
struct crypto_skcipher *tfm = ci->ci_ctfm; struct crypto_skcipher *tfm = ci->ci_ctfm;
int res = 0; int res = 0;
req = skcipher_request_alloc(tfm, GFP_NOFS); req = skcipher_request_alloc(tfm, gfp_flags);
if (!req) { if (!req) {
printk_ratelimited(KERN_ERR printk_ratelimited(KERN_ERR
"%s: crypto_request_alloc() failed\n", "%s: crypto_request_alloc() failed\n",
@ -307,9 +309,10 @@ static int ext4_page_crypto(struct inode *inode,
return 0; return 0;
} }
static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx) static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx,
gfp_t gfp_flags)
{ {
ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, GFP_NOWAIT); ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, gfp_flags);
if (ctx->w.bounce_page == NULL) if (ctx->w.bounce_page == NULL)
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
ctx->flags |= EXT4_WRITE_PATH_FL; ctx->flags |= EXT4_WRITE_PATH_FL;
@ -332,7 +335,8 @@ static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx)
* error value or NULL. * error value or NULL.
*/ */
struct page *ext4_encrypt(struct inode *inode, struct page *ext4_encrypt(struct inode *inode,
struct page *plaintext_page) struct page *plaintext_page,
gfp_t gfp_flags)
{ {
struct ext4_crypto_ctx *ctx; struct ext4_crypto_ctx *ctx;
struct page *ciphertext_page = NULL; struct page *ciphertext_page = NULL;
@ -340,17 +344,17 @@ struct page *ext4_encrypt(struct inode *inode,
BUG_ON(!PageLocked(plaintext_page)); BUG_ON(!PageLocked(plaintext_page));
ctx = ext4_get_crypto_ctx(inode); ctx = ext4_get_crypto_ctx(inode, gfp_flags);
if (IS_ERR(ctx)) if (IS_ERR(ctx))
return (struct page *) ctx; return (struct page *) ctx;
/* The encryption operation will require a bounce page. */ /* The encryption operation will require a bounce page. */
ciphertext_page = alloc_bounce_page(ctx); ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
if (IS_ERR(ciphertext_page)) if (IS_ERR(ciphertext_page))
goto errout; goto errout;
ctx->w.control_page = plaintext_page; ctx->w.control_page = plaintext_page;
err = ext4_page_crypto(inode, EXT4_ENCRYPT, plaintext_page->index, err = ext4_page_crypto(inode, EXT4_ENCRYPT, plaintext_page->index,
plaintext_page, ciphertext_page); plaintext_page, ciphertext_page, gfp_flags);
if (err) { if (err) {
ciphertext_page = ERR_PTR(err); ciphertext_page = ERR_PTR(err);
errout: errout:
@ -378,8 +382,8 @@ int ext4_decrypt(struct page *page)
{ {
BUG_ON(!PageLocked(page)); BUG_ON(!PageLocked(page));
return ext4_page_crypto(page->mapping->host, return ext4_page_crypto(page->mapping->host, EXT4_DECRYPT,
EXT4_DECRYPT, page->index, page, page); page->index, page, page, GFP_NOFS);
} }
int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk, int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
@ -398,11 +402,11 @@ int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE); BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
ctx = ext4_get_crypto_ctx(inode); ctx = ext4_get_crypto_ctx(inode, GFP_NOFS);
if (IS_ERR(ctx)) if (IS_ERR(ctx))
return PTR_ERR(ctx); return PTR_ERR(ctx);
ciphertext_page = alloc_bounce_page(ctx); ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
if (IS_ERR(ciphertext_page)) { if (IS_ERR(ciphertext_page)) {
err = PTR_ERR(ciphertext_page); err = PTR_ERR(ciphertext_page);
goto errout; goto errout;
@ -410,11 +414,12 @@ int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
while (len--) { while (len--) {
err = ext4_page_crypto(inode, EXT4_ENCRYPT, lblk, err = ext4_page_crypto(inode, EXT4_ENCRYPT, lblk,
ZERO_PAGE(0), ciphertext_page); ZERO_PAGE(0), ciphertext_page,
GFP_NOFS);
if (err) if (err)
goto errout; goto errout;
bio = bio_alloc(GFP_KERNEL, 1); bio = bio_alloc(GFP_NOWAIT, 1);
if (!bio) { if (!bio) {
err = -ENOMEM; err = -ENOMEM;
goto errout; goto errout;

6
fs/ext4/ext4.h
View file

@ -2282,11 +2282,13 @@ extern struct kmem_cache *ext4_crypt_info_cachep;
bool ext4_valid_contents_enc_mode(uint32_t mode); bool ext4_valid_contents_enc_mode(uint32_t mode);
uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size); uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size);
extern struct workqueue_struct *ext4_read_workqueue; extern struct workqueue_struct *ext4_read_workqueue;
struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode); struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode,
gfp_t gfp_flags);
void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx); void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx);
void ext4_restore_control_page(struct page *data_page); void ext4_restore_control_page(struct page *data_page);
struct page *ext4_encrypt(struct inode *inode, struct page *ext4_encrypt(struct inode *inode,
struct page *plaintext_page); struct page *plaintext_page,
gfp_t gfp_flags);
int ext4_decrypt(struct page *page); int ext4_decrypt(struct page *page);
int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk, int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
ext4_fsblk_t pblk, ext4_lblk_t len); ext4_fsblk_t pblk, ext4_lblk_t len);

14
fs/ext4/page-io.c
View file

@ -23,6 +23,7 @@
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/backing-dev.h>
#include "ext4_jbd2.h" #include "ext4_jbd2.h"
#include "xattr.h" #include "xattr.h"
@ -470,9 +471,20 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode) && if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode) &&
nr_to_submit) { nr_to_submit) {
data_page = ext4_encrypt(inode, page); gfp_t gfp_flags = GFP_NOFS;
retry_encrypt:
data_page = ext4_encrypt(inode, page, gfp_flags);
if (IS_ERR(data_page)) { if (IS_ERR(data_page)) {
ret = PTR_ERR(data_page); ret = PTR_ERR(data_page);
if (ret == ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
if (io->io_bio) {
ext4_io_submit(io);
congestion_wait(BLK_RW_ASYNC, HZ/50);
}
gfp_flags |= __GFP_NOFAIL;
goto retry_encrypt;
}
data_page = NULL; data_page = NULL;
goto out; goto out;
} }

2
fs/ext4/readpage.c
View file

@ -279,7 +279,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
if (ext4_encrypted_inode(inode) && if (ext4_encrypted_inode(inode) &&
S_ISREG(inode->i_mode)) { S_ISREG(inode->i_mode)) {
ctx = ext4_get_crypto_ctx(inode); ctx = ext4_get_crypto_ctx(inode, GFP_NOFS);
if (IS_ERR(ctx)) if (IS_ERR(ctx))
goto set_error_page; goto set_error_page;
} }