From: Omar Sandoval <[email protected]> Btrfs can transparently compress data written by the user. However, we'd like to add an interface to write pre-compressed data directly to the filesystem. This adds support for so-called "encoded writes" via pwritev2().
A new RWF_ENCODED flags indicates that a write is "encoded". If this flag is set, iov[0].iov_base points to a struct encoded_iov which contains metadata about the write: namely, the compression algorithm and the unencoded (i.e., decompressed) length of the extent. iov[0].iov_len must be set to sizeof(struct encoded_iov), which can be used to extend the interface in the future. The remaining iovecs contain the encoded extent. A similar interface for reading encoded data can be added to preadv2() in the future. Filesystems must indicate that they support encoded writes by setting FMODE_ENCODED_IO in ->file_open(). Signed-off-by: Omar Sandoval <[email protected]> --- include/linux/fs.h | 13 +++++++ include/uapi/linux/fs.h | 24 ++++++++++++- mm/filemap.c | 75 ++++++++++++++++++++++++++++++++++------- 3 files changed, 99 insertions(+), 13 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index 75c4b7680385..ae3ac0312674 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -175,6 +175,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, /* File does not contribute to nr_files count */ #define FMODE_NOACCOUNT ((__force fmode_t)0x20000000) +/* File supports encoded IO */ +#define FMODE_ENCODED_IO ((__force fmode_t)0x40000000) + /* * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector * that indicates that they should check the contents of the iovec are @@ -314,6 +317,7 @@ enum rw_hint { #define IOCB_SYNC (1 << 5) #define IOCB_WRITE (1 << 6) #define IOCB_NOWAIT (1 << 7) +#define IOCB_ENCODED (1 << 8) struct kiocb { struct file *ki_filp; @@ -3046,6 +3050,10 @@ extern int sb_min_blocksize(struct super_block *, int); extern int generic_file_mmap(struct file *, struct vm_area_struct *); extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *); extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *); +struct encoded_iov; +extern int generic_encoded_write_checks(struct kiocb *, struct encoded_iov *); +extern int import_encoded_write(struct kiocb *, struct encoded_iov *, + struct iov_iter *); extern int generic_remap_checks(struct file *file_in, loff_t pos_in, struct file *file_out, loff_t pos_out, loff_t *count, unsigned int remap_flags); @@ -3364,6 +3372,11 @@ static inline int kiocb_set_rw_flags(int rw, struct kiocb *ki, rwf_t flags) return -EOPNOTSUPP; ki->ki_flags |= IOCB_NOWAIT; } + if (flags & RWF_ENCODED) { + if (rw != WRITE || !(ki->ki_filp->f_mode & FMODE_ENCODED_IO)) + return -EOPNOTSUPP; + ki->ki_flags |= IOCB_ENCODED; + } if (flags & RWF_HIPRI) ki->ki_flags |= IOCB_HIPRI; if (flags & RWF_DSYNC) diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index aad225b05be7..b775d9aea978 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -283,6 +283,25 @@ struct fsxattr { typedef int __bitwise __kernel_rwf_t; +enum { + ENCODED_IOV_COMPRESSION_NONE, + ENCODED_IOV_COMPRESSION_ZLIB, + ENCODED_IOV_COMPRESSION_LZO, + ENCODED_IOV_COMPRESSION_ZSTD, + ENCODED_IOV_COMPRESSION_TYPES = ENCODED_IOV_COMPRESSION_ZSTD, +}; + +enum { + ENCODED_IOV_ENCRYPTION_NONE, + ENCODED_IOV_ENCRYPTION_TYPES = ENCODED_IOV_ENCRYPTION_NONE, +}; + +struct encoded_iov { + __u64 unencoded_len; + __u32 compression; + __u32 encryption; +}; + /* high priority request, poll if possible */ #define RWF_HIPRI ((__force __kernel_rwf_t)0x00000001) @@ -298,8 +317,11 @@ typedef int __bitwise __kernel_rwf_t; /* per-IO O_APPEND */ #define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) +/* encoded (e.g., compressed or encrypted) IO */ +#define RWF_ENCODED ((__force __kernel_rwf_t)0x00000020) + /* mask of flags supported by the kernel */ #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ - RWF_APPEND) + RWF_APPEND | RWF_ENCODED) #endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/filemap.c b/mm/filemap.c index 40667c2f3383..3d2555364432 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2974,24 +2974,16 @@ static int generic_write_check_limits(struct file *file, loff_t pos, return 0; } -/* - * Performs necessary checks before doing a write - * - * Can adjust writing position or amount of bytes to write. - * Returns appropriate error code that caller should return or - * zero in case that write should be allowed. - */ -inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) +static int generic_write_checks_common(struct kiocb *iocb, loff_t *count) { struct file *file = iocb->ki_filp; struct inode *inode = file->f_mapping->host; - loff_t count; int ret; if (IS_SWAPFILE(inode)) return -ETXTBSY; - if (!iov_iter_count(from)) + if (!*count) return 0; /* FIXME: this is for backwards compatibility with 2.4 */ @@ -3001,8 +2993,21 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) return -EINVAL; - count = iov_iter_count(from); - ret = generic_write_check_limits(file, iocb->ki_pos, &count); + return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count); +} + +/* + * Performs necessary checks before doing a write + * + * Can adjust writing position or amount of bytes to write. + * Returns a negative errno or the new number of bytes to write. + */ +inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) +{ + loff_t count = iov_iter_count(from); + int ret; + + ret = generic_write_checks_common(iocb, &count); if (ret) return ret; @@ -3011,6 +3016,52 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) } EXPORT_SYMBOL(generic_write_checks); +int generic_encoded_write_checks(struct kiocb *iocb, + struct encoded_iov *encoded) +{ + loff_t count = encoded->unencoded_len; + int ret; + + ret = generic_write_checks_common(iocb, &count); + if (ret) + return ret; + + if (count != encoded->unencoded_len) { + /* + * The write got truncated by generic_write_checks(). We can't + * do a partial encoded write. + */ + return -EFBIG; + } + return 0; +} +EXPORT_SYMBOL(generic_encoded_write_checks); + +/* + * If no encoding is set, this clears IOCB_ENCODED and the write should be + * treated as a normal write. + */ +int import_encoded_write(struct kiocb *iocb, struct encoded_iov *encoded, + struct iov_iter *from) +{ + if (iov_iter_single_seg_count(from) != sizeof(*encoded)) + return -EINVAL; + if (copy_from_iter(encoded, sizeof(*encoded), from) != sizeof(*encoded)) + return -EFAULT; + if (encoded->compression == ENCODED_IOV_COMPRESSION_NONE && + encoded->encryption == ENCODED_IOV_ENCRYPTION_NONE) { + iocb->ki_flags &= ~IOCB_ENCODED; + return 0; + } + if (encoded->compression > ENCODED_IOV_COMPRESSION_TYPES || + encoded->encryption > ENCODED_IOV_ENCRYPTION_TYPES) + return -EINVAL; + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + return 0; +} +EXPORT_SYMBOL(import_encoded_write); + /* * Performs necessary checks before doing a clone. * -- 2.23.0
