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    Subject[PATCH 3/3] mm: Pass FGP_NOWAIT in generic_file_buffered_read and enable ext4
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    All page-obtaining functions, which are used by ext4, look
    to go thru pagecache_get_page() path, so all taken uncharged
    pages will be properly charged. Thus, we enable AS_KEEP_MEMCG_RECLAIM
    for ext4 regular files.

    Since memcg accounting requires page lock, and function
    generic_file_buffered_read() is the only of ext4-used
    functions, which does not care about FGP_NOWAIT, we make
    it use find_get_page_flags() and pass the flag. This allows
    pagecache_get_page() to use lock_page(), when it's possible.

    Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
    ---
    fs/ext4/inode.c | 1 +
    mm/filemap.c | 8 +++++++-
    2 files changed, 8 insertions(+), 1 deletion(-)

    diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
    index b1d7ddd70eee..2fc9e4a7c0db 100644
    --- a/fs/ext4/inode.c
    +++ b/fs/ext4/inode.c
    @@ -5065,6 +5065,7 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
    inode->i_op = &ext4_file_inode_operations;
    inode->i_fop = &ext4_file_operations;
    ext4_set_aops(inode);
    + set_bit(AS_KEEP_MEMCG_RECLAIM, &inode->i_mapping->flags);
    } else if (S_ISDIR(inode->i_mode)) {
    inode->i_op = &ext4_dir_inode_operations;
    inode->i_fop = &ext4_dir_operations;
    diff --git a/mm/filemap.c b/mm/filemap.c
    index 2603c44fc74a..46922003811f 100644
    --- a/mm/filemap.c
    +++ b/mm/filemap.c
    @@ -2061,6 +2061,11 @@ static void shrink_readahead_size_eio(struct file *filp,
    ra->ra_pages /= 4;
    }

    +static int kiocb_fgp_flags(struct kiocb *iocb)
    +{
    + return (iocb->ki_flags & IOCB_NOWAIT) ? FGP_NOWAIT : 0;
    +}
    +
    /**
    * generic_file_buffered_read - generic file read routine
    * @iocb: the iocb to read
    @@ -2111,7 +2116,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
    goto out;
    }

    - page = find_get_page(mapping, index);
    + page = find_get_page_flags(mapping, index,
    + kiocb_fgp_flags(iocb));
    if (!page) {
    if (iocb->ki_flags & IOCB_NOWAIT)
    goto would_block;
    \
     
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      Last update: 2019-01-09 13:21    [W:2.666 / U:0.004 seconds]
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