| Message ID | 20180212094347.22071-6-chandan@linux.vnet.ibm.com |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | Ext4 encryption support for blocksize < pagesize | expand |
Hi Chandan, On Mon, Feb 12, 2018 at 03:13:41PM +0530, Chandan Rajendra wrote: > With block size < page size, ext4_block_write_begin() can have up to two > blocks to decrypt. Hence this commit invokes fscrypt_decrypt_block() for > each of those blocks. > > Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> > --- > fs/ext4/inode.c | 33 +++++++++++++++++++++++---------- > 1 file changed, 23 insertions(+), 10 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 69a4fd6..180dd2d 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -1158,12 +1158,13 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, > unsigned to = from + len; > struct inode *inode = page->mapping->host; > unsigned block_start, block_end; > - sector_t block; > + sector_t block, page_blk_nr; > int err = 0; > unsigned blocksize = inode->i_sb->s_blocksize; > unsigned bbits; > struct buffer_head *bh, *head, *wait[2], **wait_bh = wait; > bool decrypt = false; > + int i; > > BUG_ON(!PageLocked(page)); > BUG_ON(from > PAGE_SIZE); > @@ -1224,18 +1225,30 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, > /* > * If we issued read requests, let them complete. > */ > - while (wait_bh > wait) { > - wait_on_buffer(*--wait_bh); > - if (!buffer_uptodate(*wait_bh)) > + for (i = 0; &wait[i] < wait_bh; i++) { > + wait_on_buffer(wait[i]); > + if (!buffer_uptodate(wait[i])) > err = -EIO; > } [...] > + for (i = 0; &wait[i] < wait_bh; i++) { > + int err2; > + > + --wait_bh; > + block = page_blk_nr + (bh_offset(wait[i]) >> bbits); > + err2 = fscrypt_decrypt_block(page->mapping->host, page, > + wait[i]->b_size, > + bh_offset(wait[i]), > + block); > + if (err2) { > + clear_buffer_uptodate(wait[i]); > + err = err2; > + } > + } These are very confusing ways to iterate through an array, especially the second loop which is actually going in reverse order (why?). Why not just use a variable like 'nr_wait' for the number of valid buffer_head's like I had suggested? Then you can just do 'for (i = 0; i < nr_wait; i++)'. - Eric
On Wednesday, February 21, 2018 6:31:55 AM IST Eric Biggers wrote: > Hi Chandan, > > On Mon, Feb 12, 2018 at 03:13:41PM +0530, Chandan Rajendra wrote: > > With block size < page size, ext4_block_write_begin() can have up to two > > blocks to decrypt. Hence this commit invokes fscrypt_decrypt_block() for > > each of those blocks. > > > > Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> > > --- > > fs/ext4/inode.c | 33 +++++++++++++++++++++++---------- > > 1 file changed, 23 insertions(+), 10 deletions(-) > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 69a4fd6..180dd2d 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -1158,12 +1158,13 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, > > unsigned to = from + len; > > struct inode *inode = page->mapping->host; > > unsigned block_start, block_end; > > - sector_t block; > > + sector_t block, page_blk_nr; > > int err = 0; > > unsigned blocksize = inode->i_sb->s_blocksize; > > unsigned bbits; > > struct buffer_head *bh, *head, *wait[2], **wait_bh = wait; > > bool decrypt = false; > > + int i; > > > > BUG_ON(!PageLocked(page)); > > BUG_ON(from > PAGE_SIZE); > > @@ -1224,18 +1225,30 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, > > /* > > * If we issued read requests, let them complete. > > */ > > - while (wait_bh > wait) { > > - wait_on_buffer(*--wait_bh); > > - if (!buffer_uptodate(*wait_bh)) > > + for (i = 0; &wait[i] < wait_bh; i++) { > > + wait_on_buffer(wait[i]); > > + if (!buffer_uptodate(wait[i])) > > err = -EIO; > > } > > [...] > > > + for (i = 0; &wait[i] < wait_bh; i++) { > > + int err2; > > + > > + --wait_bh; > > + block = page_blk_nr + (bh_offset(wait[i]) >> bbits); > > + err2 = fscrypt_decrypt_block(page->mapping->host, page, > > + wait[i]->b_size, > > + bh_offset(wait[i]), > > + block); > > + if (err2) { > > + clear_buffer_uptodate(wait[i]); > > + err = err2; > > + } > > + } > > These are very confusing ways to iterate through an array, especially the second > loop which is actually going in reverse order (why?). Why not just use a > variable like 'nr_wait' for the number of valid buffer_head's like I had > suggested? Then you can just do 'for (i = 0; i < nr_wait; i++)'. > Sorry, the "--wait_bh;" part was a remanent from the "RFC PATCH V1". Without that statement, we loop in increasing order of elements in wait[] array. I will use the 'nr_wait' counter approach and post the next version of the patchset. I misunderstood your advice to mean that the code should use similar looping order in both loops.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 69a4fd6..180dd2d 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1158,12 +1158,13 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, unsigned to = from + len; struct inode *inode = page->mapping->host; unsigned block_start, block_end; - sector_t block; + sector_t block, page_blk_nr; int err = 0; unsigned blocksize = inode->i_sb->s_blocksize; unsigned bbits; struct buffer_head *bh, *head, *wait[2], **wait_bh = wait; bool decrypt = false; + int i; BUG_ON(!PageLocked(page)); BUG_ON(from > PAGE_SIZE); @@ -1224,18 +1225,30 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, /* * If we issued read requests, let them complete. */ - while (wait_bh > wait) { - wait_on_buffer(*--wait_bh); - if (!buffer_uptodate(*wait_bh)) + for (i = 0; &wait[i] < wait_bh; i++) { + wait_on_buffer(wait[i]); + if (!buffer_uptodate(wait[i])) err = -EIO; } - if (unlikely(err)) + if (unlikely(err)) { page_zero_new_buffers(page, from, to); - else if (decrypt) { - err = fscrypt_decrypt_block(page->mapping->host, page, - PAGE_SIZE, 0, page->index); - if (err) - clear_buffer_uptodate(*wait_bh); + } else if (decrypt) { + page_blk_nr = (sector_t)page->index << (PAGE_SHIFT - bbits); + + for (i = 0; &wait[i] < wait_bh; i++) { + int err2; + + --wait_bh; + block = page_blk_nr + (bh_offset(wait[i]) >> bbits); + err2 = fscrypt_decrypt_block(page->mapping->host, page, + wait[i]->b_size, + bh_offset(wait[i]), + block); + if (err2) { + clear_buffer_uptodate(wait[i]); + err = err2; + } + } } return err;
With block size < page size, ext4_block_write_begin() can have up to two blocks to decrypt. Hence this commit invokes fscrypt_decrypt_block() for each of those blocks. Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> --- fs/ext4/inode.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)