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2009-12-10exofs: Multi-device mirror supportBoaz Harrosh1-11/+27
This patch changes on-disk format, it is accompanied with a parallel patch to mkfs.exofs that enables multi-device capabilities. After this patch, old exofs will refuse to mount a new formatted FS and new exofs will refuse an old format. This is done by moving the magic field offset inside the FSCB. A new FSCB *version* field was added. In the future, exofs will refuse to mount unmatched FSCB version. To up-grade or down-grade an exofs one must use mkfs.exofs --upgrade option before mounting. Introduced, a new object that contains a *device-table*. This object contains the default *data-map* and a linear array of devices information, which identifies the devices used in the filesystem. This object is only written to offline by mkfs.exofs. This is why it is kept separate from the FSCB, since the later is written to while mounted. Same partition number, same object number is used on all devices only the device varies. * define the new format, then load the device table on mount time make sure every thing is supported. * Change I/O engine to now support Mirror IO, .i.e write same data to multiple devices, read from a random device to spread the read-load from multiple clients (TODO: stripe read) Implementation notes: A few points introduced in previous patch should be mentioned here: * Special care was made so absolutlly all operation that have any chance of failing are done before any osd-request is executed. This is to minimize the need for a data consistency recovery, to only real IO errors. * Each IO state has a kref. It starts at 1, any osd-request executed will increment the kref, finally when all are executed the first ref is dropped. At IO-done, each request completion decrements the kref, the last one to return executes the internal _last_io() routine. _last_io() will call the registered io_state_done. On sync mode a caller does not supply a done method, indicating a synchronous request, the caller is put to sleep and a special io_state_done is registered that will awaken the caller. Though also in sync mode all operations are executed in parallel. Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
2009-12-10exofs: Move all operations to an io_engineBoaz Harrosh1-53/+333
In anticipation for multi-device operations, we separate osd operations into an abstract I/O API. Currently only one device is used but later when adding more devices, we will drive all devices in parallel according to a "data_map" that describes how data is arranged on multiple devices. The file system level operates, like before, as if there is one object (inode-number) and an i_size. The io engine will split this to the same object-number but on multiple device. At first we introduce Mirror (raid 1) layout. But at the final outcome we intend to fully implement the pNFS-Objects data-map, including raid 0,4,5,6 over mirrored devices, over multiple device-groups. And more. See: http://tools.ietf.org/html/draft-ietf-nfsv4-pnfs-obj-12 * Define an io_state based API for accessing osd storage devices in an abstract way. Usage: First a caller allocates an io state with: exofs_get_io_state(struct exofs_sb_info *sbi, struct exofs_io_state** ios); Then calles one of: exofs_sbi_create(struct exofs_io_state *ios); exofs_sbi_remove(struct exofs_io_state *ios); exofs_sbi_write(struct exofs_io_state *ios); exofs_sbi_read(struct exofs_io_state *ios); exofs_oi_truncate(struct exofs_i_info *oi, u64 new_len); And when done exofs_put_io_state(struct exofs_io_state *ios); * Convert all source files to use this new API * Convert from bio_alloc to bio_kmalloc * In io engine we make use of the now fixed osd_req_decode_sense There are no functional changes or on disk additions after this patch. Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
2009-12-10exofs: move osd.c to ios.cBoaz Harrosh1-0/+125
If I do a "git mv" together with a massive code change and commit in one patch, git looses the rename and records a delete/new instead. This is bad because I want a rename recorded so later rebased/cherry-picked patches to the old name will work. Also the --follow is lost. Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>